461 U.S. 190 (1983)

PACIFIC GAS & ELECTRIC CO. ET AL.
v.
STATE ENERGY RESOURCES CONSERVATION AND DEVELOPMENT COMMISSION ET AL.

No. 81-1945.

Supreme Court of United States.

Argued January 17, 1983. Decided April 20, 1983. CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT

*192 John R. McDonough argued the cause for petitioners. With him on the briefs was Howard B. Soloway.

Deputy Solicitor General Claiborne argued the cause for the United States as amicus curiae urging reversal. With him on the brief were Solicitor General Lee, Assistant Attorney General McGrath, John H. Garvey, Leonard Schaitman, and Al J. Daniel, Jr.

Laurence H. Tribe argued the cause for respondents. With him on the brief were Roger Beers, William M. Chamberlain, Dian Grueneich, and Ralph Cavanagh.^[*]

Briefs of amici curiae urging affirmance were filed for the State of Alaska et al. by Robert Abrams, Attorney General of New York, Peter H. Schiff, and Ezra I. Bialik, Assistant Attorney General; Wilson L. Condon, Attorney General of Alaska, and Douglas K. Mertz, Assistant Attorney General; Robert K. Corbin, Attorney General of Arizona, and Anthony B. Ching, Solicitor General; John Steven Clark, Attorney General of Arkansas; Tany S. Hong, Attorney General of Hawaii, and Michael A. Lilly, First Deputy Attorney General; Robert T. Stephan, Attorney General of Kansas, Robert Vinson Eye, Assistant Attorney General, and Brian J. Moline; William J. Guste, Jr., Attorney General of Louisiana, and Kendall L. Vick, Assistant Attorney General; Warren Spannaus, Attorney General of Minnesota, and Jocelyn F. Olson, Special Assistant Attorney General; Bill Allain, Attorney General of Mississippi, and Mack Cameron, Special Assistant Attorney General; Mike Greely, Attorney General of Montana, and Mike McGrath, Assistant Attorney General; Richard H. Bryan, Attorney General of Nevada, and Larry Struve, Chief Deputy Attorney General; William J. Brown, Attorney General of Ohio, and E. Dennis Muchnicki, Assistant Attorney General; Jan Eric Cartwright, Attorney General of Oklahoma, and Sara J. Drake, Assistant Attorney General; Daniel R. McLeod, Attorney General of South Carolina, and Richard P. Wilson, Assistant Attorney General; John J. Easton, Jr., Attorney General of Vermont, and Merideth Wright, Assistant Attorney General; Chauncey H. Browning, Attorney General of West Virginia, and Robert R. Rodecker; Steven F. Freudenthal, Attorney General of Wyoming, and Walter Perry III, Senior Assistant Attorney General; for the State of Connecticut by Carl R. Ajello, Attorney General, Robert S. Golden, Jr., Assistant Attorney General, and Neil T. Proto, Special Assistant Attorney General; for the State of Maine by James E. Tierney, Attorney General, Rufus E. Brown, Deputy Attorney General, H. Cabanne Howard, Senior Assistant Attorney General, and Gregory W. Sample, Assistant Attorney General; for the Commonwealth of Massachusetts by Francis X. Bellotti, Attorney General, and Stephen M. Leonard, Assistant Attorney General; for the State of Illinois et al. by Gregory H. Smith, Attorney General of New Hampshire, E. Tupper Kinder, Assistant Attorney General, Tyrone C. Fahner, Attorney General of Illinois, and John Van Vranken, Anne Rapkin, and Jeffrey C. Paulson, Assistant Attorneys General; for the State of Oregon by Dave Frohnmayer, Attorney General, Stanton F. Long, Deputy Attorney General, William F. Gary, Solicitor General, James E. Mountain, Jr., Deputy Solicitor General, and Frank W. Ostrander, Jr., Assistant Attorney General; for the State of Washington by Kenneth O. Eikenberry, Attorney General, and Edward B. Mackie, Chief Deputy Attorney General; for the State of Wisconsin et al. by Bronson C. La Follette, Attorney General of Wisconsin, Steven M. Schur, and Carl A. Sinderbrand, Assistant Attorney General; Rufus L. Edmisten, Attorney General of North Carolina; John Ashcroft, Attorney General of Missouri; Steven L. Beshear, Attorney General of Kentucky; Richard H. Levin, Attorney General of New Mexico, and Geoffrey W. Sloan; Thomas J. Miller, Attorney General of Iowa, and James R. Maret; Leroy S. Zimmerman, Attorney General of Pennsylvania; for the Public Utilities Commission of the State of California et al. by Janice E. Kerr, J. Calvin Simpson, and Paul Rodgers.

Joseph D. Alviani filed a brief for the New England Legal Foundation as amicus curiae.

*193 JUSTICE WHITE delivered the opinion of the Court.

The turning of swords into plowshares has symbolized the transformation of atomic power into a source of energy in *194 American society. To facilitate this development the Federal Government relaxed its monopoly over fissionable materials and nuclear technology, and in its place, erected a complex scheme to promote the civilian development of nuclear energy, while seeking to safeguard the public and the environment from the unpredictable risks of a new technology. Early on, it was decided that the States would continue their traditional role in the regulation of electricity production. The interrelationship of federal and state authority in the nuclear energy field has not been simple; the federal regulatory structure has been frequently amended to optimize the partnership.

This case emerges from the intersection of the Federal Government's efforts to ensure that nuclear power is safe with the exercise of the historic state authority over the generation and sale of electricity. At issue is whether provisions in the 1976 amendments to California's Warren-Alquist Act, Cal. Pub. Res. Code Ann. §§ 25524.1(b) and 25524.2 (West 1977), which condition the construction of nuclear plants on findings by the State Energy Resources Conservation and Development Commission that adequate storage facilities and means of disposal are available for nuclear waste, *195 are pre-empted by the Atomic Energy Act of 1954, 68 Stat. 919, as amended, 42 U. S. C. § 2011 et seq.

I

A nuclear reactor must be periodically refueled and the "spent fuel" removed. This spent fuel is intensely radioactive and must be carefully stored. The general practice is to store the fuel in a water-filled pool at the reactor site. For many years, it was assumed that this fuel would be reprocessed; accordingly, the storage pools were designed as short-term holding facilities with limited storage capacities. As expectations for reprocessing remained unfulfilled, the spent fuel accumulated in the storage pools, creating the risk that nuclear reactors would have to be shut down. This could occur if there were insufficient room in the pool to store spent fuel and also if there were not enough space to hold the entire fuel core when certain inspections or emergencies required unloading of the reactor. In recent years, the problem has taken on special urgency. Some 8,000 metric tons of spent nuclear fuel have already accumulated, and it is projected that by the year 2000 there will be some 72,000 metric tons of spent fuel.^[1] Government studies indicate that a number of reactors could be forced to shut down in the near future due to the inability to store spent fuel.^[2]

*196 There is a second dimension to the problem. Even with water pools adequate to store safely all the spent fuel produced during the working lifetime of the reactor, permanent disposal is needed because the wastes will remain radioactive for thousands of years.^[3] A number of long-term nuclear waste management strategies have been extensively examined. These range from sinking the wastes in stable deep seabeds, to placing the wastes beneath ice sheets in Greenland and Antarctica, to ejecting the wastes into space by rocket. The greatest attention has been focused on disposing of the wastes in subsurface geologic repositories such as salt deposits.^[4] Problems of how and where to store nuclear wastes has engendered considerable scientific, political, and public debate. There are both safety and economic aspects to the nuclear waste issue: first, if not properly stored, nuclear wastes might leak and endanger both the environment and human health;^[5] second, the lack of a long-term disposal option increases the risk that the insufficiency of interim storage space for spent fuel will lead to reactor shutdowns, *197 rendering nuclear energy an unpredictable and uneconomical adventure.^[6]

The California laws at issue here are responses to these concerns. In 1974, California adopted the Warren-Alquist State Energy Resources Conservation and Development Act, Cal. Pub. Res. Code Ann. § 25000-25986 (West 1977 and Supp. 1983). The Act requires that a utility seeking to build in California any electric power generating plant, including a nuclear powerplant, must apply for certification to the State Energy Resources Conservation and Development Commission (Energy Commission).^[7] The Warren-Alquist Act was amended in 1976 to provide additional state regulation of new nuclear powerplant construction.

Two sections of these amendments are before us. Section 25524.1(b) provides that before additional nuclear plants may be built, the Energy Commission must determine on a case-by-case basis that there will be "adequate capacity" for storage of a plant's spent fuel rods "at the time such nuclear facility requires such . . . storage." The law also requires that each utility provide continuous, on-site, "full core reserve storage capacity" in order to permit storage of the entire reactor *198 core if it must be removed to permit repairs of the reactor. In short, § 25524.1(b) addresses the interim storage of spent fuel.

Section 25524.2 deals with the long-term solution to nuclear wastes. This section imposes a moratorium on the certification of new nuclear plants until the Energy Commission "finds that there has been developed and that the United States through its authorized agency has approved and there exists a demonstrated technology or means for the disposal of high-level nuclear waste." "Disposal" is defined as a "method for the permanent and terminal disposition of high-level nuclear waste . . . ." §§ 25524.2(a), (c). Such a finding must be reported to the state legislature, which may nullify it.^[8]

In 1978, petitioners Pacific Gas & Electric Co. and Southern California Edison Co. filed this action in the United States District Court, requesting a declaration that numerous provisions of the Warren-Alquist Act, including the two sections challenged here, are invalid under the Supremacy Clause because they are pre-empted by the Atomic Energy Act. The District Court held that petitioners had standing to challenge §§ 25524.1(b) and 25524.2,^[9] that the issues presented by these two statutes are ripe for adjudication, and that the two provisions are void because they are pre-empted by and in conflict with the Atomic Energy Act. 489 F. Supp. 699 (ED Cal. 1980).

*199 The Court of Appeals for the Ninth Circuit affirmed the District Court's ruling that the petitioners have standing to challenge the California statutes, and also agreed that the challenge to § 25524.2 is ripe for review. It concluded, however, that the challenge to § 25524.1(b) was not ripe "[b]ecause we cannot know whether the Energy Commission will ever find a nuclear plant's storage capacity to be inadequate. . . ." 659 F. 2d 903, 918 (1981).^[10] On the merits, the court held that the nuclear moratorium provisions of § 25524.2 were not pre-empted because §§ 271 and 274(k) of the Atomic Energy Act, 42 U. S. C. §§ 2018 and 2021(k), constitute a congressional authorization for States to regulate nuclear powerplants "for purposes other than protection against radiation hazards."^[11] The court held that § 25524.2 was not designed to provide protection against radiation hazards, but *200 was adopted because "uncertainties in the nuclear fuel cycle make nuclear power an uneconomical and uncertain source of energy." 659 F. 2d, at 925. Nor was the provision invalid as a barrier to fulfillment of the federal goal of encouraging the development of atomic energy. The granting of state authority in §§ 271 and 274(k), combined with recent federal enactments, demonstrated that Congress did not intend that nuclear power be developed "at all costs," but only that it proceed consistent with other priorities and subject to controls traditionally exercised by the States and expressly preserved by the federal statute.^[12]

We granted certiorari limited to the questions of whether §§ 25524.1(b) and 25524.2 are ripe for judicial review, and whether they are pre-empted by the Atomic Energy Act. 457 U. S. 1132 (1982).

II

We agree that the challenge to § 25524.2 is ripe for judicial review, but that the questions concerning § 25524.1(b) are not. The basic rationale of the ripeness doctrine "is to prevent the courts, through avoidance of premature adjudication, from entangling themselves in abstract disagreements over administrative policies, and also to protect the agencies from judicial interference until an administrative decision has been formalized and its effects felt in a concrete way by the challenging parties." Abbott Laboratories v. Gardner, 387 *201 U. S. 136, 148-149 (1967). In Abbott Laboratories, which remains our leading discussion of the doctrine, we indicated that the question of ripeness turns on "the fitness of the issues for judicial decision" and "the hardship to the parties of withholding court consideration." Id., at 149.

Both of these factors counsel in favor of finding the challenge to the waste disposal regulations in § 25524.2 ripe for adjudication. The question of pre-emption is predominantly legal, and although it would be useful to have the benefit of California's interpretation of what constitutes a demonstrated technology or means for the disposal of high-level nuclear waste, resolution of the pre-emption issue need not await that development. Moreover, postponement of decision would likely work substantial hardship on the utilities. As the Court of Appeals cogently reasoned, for the utilities to proceed in hopes that, when the time for certification came, either the required findings would be made or the law would be struck down, requires the expenditures of millions of dollars over a number of years, without any certainty of recovery if certification were denied.^[13] The construction of new nuclear facilities requires considerable advance planning — on the order of 12 to 14 years.^[14] Thus, as in the Rail Reorganization Act Cases, 419 U. S. 102, 144 (1974), "decisions to be made now or in the short future may be affected" by whether we act. " `One does not have to await the consummation of threatened injury to obtain preventive relief. If the injury is certainly impending that is enough.' " Id., at 143, quoting Pennsylvania v. West Virginia, 262 U. S. 553, 593 (1923). To require the industry to proceed without knowing whether the moratorium is valid would impose a palpable *202 and considerable hardship on the utilities, and may ultimately work harm on the citizens of California. Moreover, if petitioners are correct that § 25524.2 is void because it hinders the commercial development of atomic energy, "delayed resolution would frustrate one of the key purposes of the [Atomic Energy] Act." Duke Power Co. v. Carolina Environmental Study Group, Inc., 438 U. S. 59, 82 (1978). For these reasons, the issue of whether § 25524.2 is pre-empted by federal law should be decided now.^[15]

*203 Questions concerning the constitutionality of the interim storage provision, § 25524.1(b), however, are not ripe for review. While the waste disposal statute operates on a state-wide basis, the Energy Commission is directed to make determinations under § 25524.1(b) on a case-by-case basis. As the Court of Appeals explained, because "we cannot know whether the Energy Commission will ever find a nuclear plant's storage capacity to be inadequate," judicial consideration of this provision should await further developments.^[16] Furthermore, because we hold today that § 25524.2 is not pre-empted by federal law, there is little likelihood that industry behavior would be uniquely affected by whatever uncertainty surrounds the interim storage provisions. In these circumstances, a court should not stretch to reach an early, and perhaps premature, decision respecting § 25524.1(b).

III

It is well established that within constitutional limits Congress may pre-empt state authority by so stating in express terms. Jones v. Rath Packing Co., 430 U. S. 519, 525 (1977). Absent explicit pre-emptive language, Congress' intent *204 to supersede state law altogether may be found from a " `scheme of federal regulation . . . so pervasive as to make reasonable the inference that Congress left no room for the States to supplement it,' because `the Act of Congress may touch a field in which the federal interest is so dominant that the federal system will be assumed to preclude enforcement of state laws on the same subject,' or because `the object sought to be obtained by the federal law and the character of obligations imposed by it may reveal the same purpose.' " Fidelity Federal Savings & Loan Assn. v. De la Cuesta, 458 U. S. 141, 153 (1982), quoting Rice v. Santa Fe Elevator Corp., 331 U. S. 218, 230 (1947). Even where Congress has not entirely displaced state regulation in a specific area, state law is pre-empted to the extent that it actually conflicts with federal law. Such a conflict arises when "compliance with both federal and state regulations is a physical impossibility," Florida Lime & Avocado Growers, Inc. v. Paul, 373 U. S. 132, 142-143 (1963), or where state law "stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress." Hines v. Davidowitz, 312 U. S. 52, 67 (1941).

Petitioners, the United States, and supporting amici, present three major lines of argument as to why § 25524.2 is pre-empted. First, they submit that the statute — because it regulates construction of nuclear plants and because it is allegedly predicated on safety concerns — ignores the division between federal and state authority created by the Atomic Energy Act, and falls within the field that the Federal Government has preserved for its own exclusive control. Second, the statute, and the judgments that underlie it, conflict with decisions concerning the nuclear waste disposal issue made by Congress and the Nuclear Regulatory Commission. Third, the California statute frustrates the federal goal of developing nuclear technology as a source of energy. We consider each of these contentions in turn.

*205 A

Even a brief perusal of the Atomic Energy Act reveals that, despite its comprehensiveness, it does not at any point expressly require the States to construct or authorize nuclear powerplants or prohibit the States from deciding, as an absolute or conditional matter, not to permit the construction of any further reactors. Instead, petitioners argue that the Act is intended to preserve the Federal Government as the sole regulator of all matters nuclear, and that § 25524.2 falls within the scope of this impliedly pre-empted field. But as we view the issue, Congress, in passing the 1954 Act and in subsequently amending it, intended that the Federal Government should regulate the radiological safety aspects involved in the construction and operation of a nuclear plant, but that the States retain their traditional responsibility in the field of regulating electrical utilities for determining questions of need, reliability, cost, and other related state concerns.

Need for new power facilities, their economic feasibility, and rates and services, are areas that have been characteristically governed by the States. Justice Brandeis once observed that the "franchise to operate a public utility . . . is a special privilege which . . . may be granted or withheld at the pleasure of the State." Frost v. Corporation Comm'n, 278 U. S. 515, 534 (1929) (dissenting opinion). "The nature of government regulation of private utilities is such that a utility may frequently be required by the state regulatory scheme to obtain approval for practices a business regulated in less detail would be free to institute without any approval from a regulatory body." Jackson v. Metropolitan Edison Co., 419 U. S. 345, 357 (1974). See Central Hudson Gas & Electric Corp. v. Public Service Comm'n of New York, 447 U. S. 557, 569 (1980) ("The State's concern that rates be fair and efficient represents a clear and substantial governmental interest"). With the exception of the broad authority of the *206 Federal Power Commission, now the Federal Energy Regulatory Commission, over the need for and pricing of electrical power transmitted in interstate commerce, see Federal Power Act, 16 U. S. C. § 824 (1976 ed. and Supp. V), these economic aspects of electrical generation have been regulated for many years and in great detail by the States.^[17] As we noted in Vermont Yankee Nuclear Power Corp. v. Natural Resources Defense Council, Inc., 435 U. S. 519, 550 (1978): "There is little doubt that under the Atomic Energy Act of 1954, state public utility commissions or similar bodies are empowered to make the initial decision regarding the need for power." Thus, "Congress legislated here in a field which the States have traditionally occupied. . . . So we start with the assumption that the historic police powers of the States were not to be superseded by the Federal Act unless that was the clear and manifest purpose of Congress." Rice v. Santa Fe Elevator Corp., supra, at 230.

The Atomic Energy Act must be read, however, against another background. Enrico Fermi demonstrated the first nuclear reactor in 1942, and Congress authorized civilian application of atomic power in 1946, Atomic Energy Act of 1946, see Act of Aug. 1, 1946, 60 Stat. 755, at which time the Atomic Energy Commission (AEC) was created. Until 1954, however, the use, control, and ownership of nuclear technology remained a federal monopoly. The Atomic Energy Act of 1954, Act of Aug. 30, 1954, 68 Stat. 919, as *207 amended, 42 U. S. C. § 2011 et seq. (1976 ed. and Supp. V), grew out of Congress' determination that the national interest would be best served if the Government encouraged the private sector to become involved in the development of atomic energy for peaceful purposes under a program of federal regulation and licensing. See H. R. Rep. No. 2181, 83d Cong., 2d Sess., 1-11 (1954). The Act implemented this policy decision by providing for licensing of private construction, ownership, and operation of commercial nuclear power reactors. Duke Power Co. v. Carolina Environmental Study Group, Inc., 438 U. S., at 63. The AEC, however, was given exclusive jurisdiction to license the transfer, delivery, receipt, acquisition, possession, and use of nuclear materials. 42 U. S. C. §§ 2014(e), (z), (aa), 2061-2064, 2071-2078, 2091-2099, 2111-2114 (1976 ed. and Supp. V). Upon these subjects, no role was left for the States.

The Commission, however, was not given authority over the generation of electricity itself, or over the economic question whether a particular plant should be built. We observed in Vermont Yankee, supra, at 550, that "[t]he Commission's prime area of concern in the licensing context, . . . is national security, public health, and safety." See also Power Reactor Development Co. v. Electrical Workers, 367 U. S. 396, 415 (1961) (utility's investment not to be considered by Commission in its licensing decisions). The Nuclear Regulatory Commission (NRC), which now exercises the AEC's regulatory authority, does not purport to exercise its authority based on economic considerations, 10 CFR § 8.4 (1982), and has recently repealed its regulations concerning the financial qualifications and capabilities of a utility proposing to construct and operate a nuclear powerplant. 47 Fed. Reg. 13751 (1982). In its notice of rule repeal, the NRC stated that utility financial qualifications are only of concern to the NRC if related to the public health and safety.^[18] It is *208 almost inconceivable that Congress would have left a regulatory vacuum; the only reasonable inference is that Congress intended the States to continue to make these judgments. Any doubt that ratemaking and plant-need questions were to remain in state hands was removed by § 271, 42 U. S. C. § 2018, which provided:

"Nothing in this chapter shall be construed to affect the authority or regulations of any Federal, State or local agency with respect to the generation, sale, or transmission of electric power produced through the use of nuclear facilities licensed by the Commission . . . ."

The legislative Reports accompanying this provision do little more than restate the statutory language, S. Rep. No. 1699, 83d Cong., 2d Sess., 31 (1954); H. R. Rep. No. 2181, supra, at 31, but statements on the floor of Congress confirm that while the safety of nuclear technology was the exclusive business of the Federal Government, state power over the production of electricity was not otherwise displaced.^[19]

The 1959 amendments reinforced this fundamental division of authority. In 1959, Congress amended the Atomic Energy Act in order to "clarify the respective responsibilities *209. . . of the States and the Commission with respect to the regulation of byproduct, source, and special nuclear materials." 42 U. S. C. § 2021(a)(1). See S. Rep. No. 870, 86th Cong., 1st Sess., 8, 10-12 (1959). The authority of the States over the planning for new powerplants and ratemaking were not at issue. Indeed, the point of the 1959 Amendments was to heighten the States' role. Section 274(b), 42 U. S. C. § 2021(b), authorized the NRC, by agreements with state governors to discontinue its regulatory authority over certain nuclear materials under limited conditions.^[20] State programs permitted under the amendment were required to be "coordinated and compatible" with that of the NRC. § 2021(g); S. Rep. No. 870, supra, at 11. The subject matters of those agreements were also limited by § 274(c), 42 U. S. C. § 2021(c), which states:

"[T]he Commission shall retain authority and responsibility with respect to regulation of —

"(1) the construction and operation of any production or utilization facility;

.....

"(4) the disposal of such . . . byproduct, source, or special nuclear material as the Commission determines. . . should, because of the hazards or potential hazards thereof, not be so disposed of without a license from the Commission."

Although the authority reserved by § 274(c) was exclusively for the Commission to exercise, see S. Rep. No. 870, supra, at 8, 9; H. R. Rep. No. 1125, 86th Cong., 1st Sess., 8, 9 (1959), Congress made clear that the section was not intended to cut back on pre-existing state authority outside the *210 NRC's jurisdiction.^[21] Section 274(k), 42 U. S. C. § 2021(k), states:

"Nothing in this section shall be construed to affect the authority of any State or local agency to regulate activities for purposes other than protection against radiation hazards."

Section 274(k), by itself, limits only the pre-emptive effect of "this section," that is, § 274, and does not represent an affirmative grant of power to the States. But Congress, by permitting regulation "for purposes other than protection against radiation hazards" underscored the distinction drawn in 1954 between the spheres of activity left respectively to the Federal Government and the States.

This regulatory structure has remained unchanged, for our purposes, until 1965, when the following proviso was added to § 271:

"Provided, that this section shall not be deemed to confer upon any Federal, State or local agency any authority to regulate, control, or restrict any activities of the Commission."

The accompanying Report by the Joint Committee on Atomic Energy makes clear that the amendment was not intended to detract from state authority over energy facilities.^[22] Instead, *211 the proviso was added to overrule a Court of Appeals opinion which interpreted § 271 to allow a municipality to prohibit transmission lines necessary for the AEC's own activities. Maun v. United States, 347 F. 2d 970 (CA9 1965). There is no indication that Congress intended any broader limitation of state regulatory power over utility companies. Indeed, Reports and debates accompanying the 1965 amendment indicate that § 271's purpose "was to make it absolutely clear that the Atomic Energy Act's special provisions on licensing of reactors did not disturb the status quo with respect to the then existing authority of Federal, State, and local bodies to regulate generation, sale, or transmission of electric power." 111 Cong. Rec. 19822 (1965) (statement of Sen. Hickenlooper).^[23]

This account indicates that from the passage of the Atomic Energy Act in 1954, through several revisions, and to the present day, Congress has preserved the dual regulation of *212 nuclear-powered electricity generation: the Federal Government maintains complete control of the safety and "nuclear" aspects of energy generation; the States exercise their traditional authority over the need for additional generating capacity, the type of generating facilities to be licensed, land use, ratemaking, and the like.^[24]

The above is not particularly controversial. But deciding how § 25524.2 is to be construed and classified is a more difficult proposition. At the outset, we emphasize that the statute does not seek to regulate the construction or operation of a nuclear powerplant. It would clearly be impermissible for California to attempt to do so, for such regulation, even if enacted out of nonsafety concerns, would nevertheless directly conflict with the NRC's exclusive authority over plant construction and operation. Respondents appear to concede as much. Respondents do broadly argue, however, that although safety regulation of nuclear plants by States is forbidden, a State may completely prohibit new construction until its safety concerns are satisfied by the Federal Government. We reject this line of reasoning. State safety regulation is not pre-empted only when it conflicts with federal law. Rather, the Federal Government has occupied the entire field of nuclear safety concerns, except the limited powers expressly ceded to the States.^[25] When the Federal Government *213 completely occupies a given field or an identifiable portion of it, as it has done here, the test of pre-emption is whether "the matter on which the State asserts the right to act is in any way regulated by the Federal Act." Rice v. Santa Fe Elevator Corp., 331 U. S., at 236. A state moratorium on nuclear construction grounded in safety concerns falls squarely within the prohibited field. Moreover, a state judgment that nuclear power is not safe enough to be further developed would conflict directly with the countervailing judgment of the NRC, see, infra, at 218-219, that nuclear construction may proceed notwithstanding extant uncertainties as to waste disposal. A state prohibition on nuclear construction for safety reasons would also be in the teeth of the Atomic Energy Act's objective to insure that nuclear technology be safe enough for widespread development and use — and would be pre-empted for that reason. Infra, at 221-222.

That being the case, it is necessary to determine whether there is a nonsafety rationale for § 25524.2. California has maintained, and the Court of Appeals agreed, that § 25524.2 was aimed at economic problems, not radiation hazards. The California Assembly Committee on Resources, Land Use, and Energy, which proposed a package of bills including § 25524.2, reported that the waste disposal problem was "largely economic or the result of poor planning, not safety related." Reassessment of Nuclear Energy in California: A Policy Analysis of Proposition 15 and its Alternatives, p. 18 (1976) (Reassessment Report) (emphasis in original). The Committee explained that the lack of a federally approved method of waste disposal created a "clog" in the nuclear fuel cycle. Storage space was limited while more nuclear wastes were continuously produced. Without a permanent means of disposal, the nuclear waste problem could become critical, *214 leading to unpredictably high costs to contain the problem or, worse, shutdowns in reactors. "Waste disposal safety," the Reassessment Report notes, "is not directly addressed by the bills, which ask only that a method [of waste disposal] be chosen and accepted by the federal government." Id., at 156 (emphasis in original).

The Court of Appeals adopted this reading of § 25524.2. Relying on the Reassessment Report, the court concluded:

"[S]ection 25524.2 is directed towards purposes other than protection against radiation hazards. While Proposition 15 would have required California to judge the safety of a proposed method of waste disposal, section 25524.2 leaves that judgment to the federal government. California is concerned not with the adequacy of the method, but rather with its existence." 659 F. 2d, at 925.

Our general practice is to place considerable confidence in the interpretations of state law reached by the federal courts of appeals. Cf. Mills v. Rogers, 457 U. S. 291, 306 (1982); Bishop v. Wood, 426 U. S. 341, 346 (1976). Petitioners and amici nevertheless attempt to upset this interpretation in a number of ways. First, they maintain that § 25524.2 evinces no concern with the economics of nuclear power. The statute states that the "development" and "existence" of a permanent disposal technology approved by federal authorities will lift the moratorium; the statute does not provide for considering the economic costs of the technology selected. This view of the statute is overly myopic. Once a technology is selected and demonstrated, the utilities and the California Public Utilities Commission would be able to estimate costs; such cost estimates cannot be made until the Federal Government has settled upon the method of long-term waste disposal. Moreover, once a satisfactory disposal technology is found and demonstrated, fears of having to close down operating reactors should largely evaporate.

*215 Second, it is suggested that California, if concerned with economics, would have banned California utilities from building plants outside the State. This objection carries little force. There is no indication that California utilities are contemplating such construction; the state legislature is not obligated to address purely hypothetical facets of a problem.

Third, petitioners note that there already is a body, the California Public Utilities Commission, which is authorized to determine on economic grounds whether a nuclear powerplant should be constructed.^[26] While California is certainly free to make these decisions on a case-by-case basis, a State is not foreclosed from reaching the same decision through a legislative judgment, applicable to all cases. The economic uncertainties engendered by the nuclear waste disposal problems are not factors that vary from facility to facility; the issue readily lends itself to more generalized decisionmaking and California cannot be faulted for pursuing that course.

Fourth, petitioners note that Proposition 15, the initiative out of which § 25524.2 arose, and companion provisions in California's so-called nuclear laws, are more clearly written with safety purposes in mind.^[27] It is suggested that § 25524.2 shares a common heritage with these laws and should be presumed to have been enacted for the same purposes. *216 The short answer here is that these other state laws are not before the Court, and indeed, Proposition 15 was not passed; these provisions and their pedigree do not taint other parts of the Warren-Alquist Act.

Although these specific indicia of California's intent in enacting § 25524.2 are subject to varying interpretation, there are two further reasons why we should not become embroiled in attempting to ascertain California's true motive. First, inquiry into legislative motive is often an unsatisfactory venture. United States v. O'Brien, 391 U. S. 367, 383 (1968). What motivates one legislator to vote for a statute is not necessarily what motivates scores of others to enact it. Second, it would be particularly pointless for us to engage in such inquiry here when it is clear that the States have been allowed to retain authority over the need for electrical generating facilities easily sufficient to permit a State so inclined to halt the construction of new nuclear plants by refusing on economic grounds to issue certificates of public convenience in individual proceedings. In these circumstances, it should be up to Congress to determine whether a State has misused the authority left in its hands.

Therefore, we accept California's avowed economic purpose as the rationale for enacting § 25524.2. Accordingly, the statute lies outside the occupied field of nuclear safety regulation.^[28]

*217 B

Petitioners' second major argument concerns federal regulation aimed at the nuclear waste disposal problem itself. It is contended that § 25524.2 conflicts with federal regulation of nuclear waste disposal, with the NRC's decision that it is permissible to continue to license reactors, notwithstanding uncertainty surrounding the waste disposal problem, and with Congress' recent passage of legislation directed at that problem.

Pursuant to its authority under the Act, 42 U. S. C. §§ 2071-2075, 2111-2114 (1976 ed. and Supp. V), the AEC, and later the NRC, promulgated extensive and detailed regulations concerning the operation of nuclear facilities and the handling of nuclear materials. The following provisions are relevant to the spent fuel and waste disposal issues in this case. To receive an NRC operating license, one must submit a safety analysis report, which includes a "radioactive waste handling syste[m]." 10 CFR § 50.34(b)(2)(i), (ii) (1982). See also 10 CFR § 150.15(a)(1)(i) (1982). The regulations specify general design criteria and control requirements for fuel storage and handling and radioactive waste to be stored at the reactor site. 10 CFR pt. 50, App. A, Criteria 60-64, p. 412 (1982). In addition, the NRC has promulgated detailed regulations governing storage and disposal away from the reactor. 10 CFR pt. 72 (1982). NRC has also promulgated procedural requirements covering license applications for disposal of high-level radioactive waste in geologic repositories. 10 CFR pt. 60 (1982).

Congress gave the Department of Energy the responsibility for "the establishment of temporary and permanent facilities for storage, management, and ultimate disposal of nuclear wastes." 42 U. S. C. § 7133(a)(8)(C) (1976 ed., *218 Supp. V). No such permanent disposal facilities have yet been licensed, and the NRC and the Department of Energy continue to authorize the storage of spent fuel at reactor sites in pools of water. In 1977, the NRC was asked by the Natural Resources Defense Council to halt reactor licensing until it had determined that there was a method of permanent disposal for high-level waste. The NRC concluded that, given the progress toward the development of disposal facilities and the availability of interim storage, it could continue to license new reactors. Natural Resources Defense Council, Inc. v. NRC, 582 F. 2d 166, 168-169 (CA2 1978).

The NRC's imprimatur, however, indicates only that it is safe to proceed with such plants, not that it is economically wise to do so.^[29] Because the NRC order does not and could *219 not compel a utility to develop a nuclear plant, compliance with both it and § 25524.2 is possible. Moreover, because the NRC's regulations are aimed at insuring that plants are safe, not necessarily that they are economical, § 25524.2 does not interfere with the objective of the federal regulation.

Nor has California sought through § 25524.2 to impose its own standards on nuclear waste disposal. The statute accepts that it is the federal responsibility to develop and license such technology. As there is no attempt on California's part to enter this field, one which is occupied by the Federal Government, we do not find § 25524.2 pre-empted any more by the NRC's obligations in the waste disposal field than by its licensing power over the plants themselves.

After this case was decided by the Court of Appeals, a new piece was added to the regulatory puzzle. In its closing week, the 97th