The Wilderness Society Alaska Center for the Environment v. United States Fish & Wildlife Service

*1055 OPINION

We consider an action brought by the Wilderness Society and the Alaska Center for the Environment (“Plaintiffs”) challenging a decision by the United States Fish and Wildlife Service (“USFWS”), to grant a permit for a sockeye salmon enhancement project (“Enhancement Project”) that annually introduces about six million hatchery-reared salmon fry into Tustumena Lake, the largest freshwater lake in the Kenai National Wildlife Refuge (“Kenai Refuge”) and the Kenai Wilderness. Plaintiffs assert that the USFWS permit for the Enhancement Project violated the Wilderness Act, 16 U.S.C. §§ 1131-1136, by offending its mandate to preserve the “natural conditions” that are a part of the “wilderness character” of the Kenai Wilderness, id. §§ 1131, 1133, and by sanctioning an impermissible “commercial enterprise” within a designated wilderness area. Id. § 1133(c). Plaintiffs also claim that the Enhancement Project violates the National Wildlife Refuge Administration Act of 1966, 16 U.S.C. §§ 668dd-668ee (“Refuge Act”), because the project is not consistent with the purposes of the Kenai Refuge as set forth in the Refuge Act. Id. § 668dd. The district court denied Plaintiffs’ motion for summary judgment and sua sponte entered summary judgment in favor of the USFWS. After final judgment was entered a timely appeal followed. We have jurisdiction pursuant to 28 U.S.C. § 1331. We conclude that the district court erred in finding that the Enhancement Project is not a “commercial enterprise” that Congress prohibited within the designated wilderness. We reverse and remand so that the final decision of the USFWS may be set aside, the Enhancement Project enjoined, and judgment entered for Plaintiffs.

I

A

The area now known as the Kenai Refuge has been recognized as protected wilderness by the federal government for more than sixty years. 1 In 1941, President Franklin D. Roosevelt issued an Executive Order designating about two million acres of land on Alaska’s Kenai Peninsula, including Tustumena Lake, as the Kenai National Moose Range for the purpose of “protecting the natural breeding and feeding range of the giant Kenai moose.” Exec. Order No. 8979, 6 Fed. Reg. 6471 (Dec. 16, 1941).

In 1964 Congress passed the Wilderness Act, which established the National Wilderness Preservation System with the explicit statutory purpose “to assure that an increasing population, accompanied by expanding settlement and growing mechanization, does not occupy and modify all areas within the United States and its possessions, leaving no lands designated for preservation and protection in their natural condition.” 16 U.S.C. § 1131(a). Congress thereby expressed support for the principle that wilderness has value to society that requires conservation and preservation. As President Lyndon B. Johnson reportedly said upon signing of the Wilderness Act in 1964, “[i]f future generations are to remember us with gratitude rather than contempt, we must leave them more than the miracles of technology. We must leave them a glimpse of the world as it was in the beginning, not just after we got through with it.” National Park Service, Grand Canyon National Park Wilderness Management Plan 1-2 (1989), available at http://www.nps.gov/grca/wilderness/doeu-ments/ sec-one.pdf. 2

The Wilderness Act required the Secretary of the Interior to make recommenda *1056 tions to the President as to the suitability of existing national parks, refuges, and game ranges for preservation as wilderness. 16 U.S.C. § 1132(c). Upon recommendation of the President, Congress was empowered to designate existing national park, wildlife refuge, and game range lands as wilderness. Id. 3

Two years after enacting the Wilderness Act, Congress passed the Refuge Act for the purpose of “consolidating the authorities relating to the various categories of areas that are administered ... for the conservation of fish and wildlife.” 16 U.S.C. § 668dd(a)(l). In furtherance of this goal, the Refuge Act established the “National Wildlife Refuge System,” under the administration of USFWS. Id.

In 1980, Congress enacted the Alaska National Interest Lands Conservation Act (“ANILCA”), Pub.L. No. 96-487, Title III, § 702(7), 94 Stat. 2371 (1980), to control the management of Alaska refuge lands. ANILCA expanded the Kenai National Moose Range by nearly a quarter-million acres, renamed it the Kenai National Wildlife Refuge, ANILCA § 303(4); 16 U.S.C. § 668dd notes, and further set aside 1.35 million acres of the Refuge, including Tus-tumena Lake, as the Kenai Wilderness, a designated wilderness pursuant to Congress’s authority to protect lands under § 1132(c) of the Wilderness Act. ANILCA § 702(7); 16 U.S.C. § 1132(c) & notes. ANILCA recited that the purposes of the Kenai Refuge encompass, among other aims, the “conserv[ation of] fish and wildlife populations and habitats in their natural diversity.” ANILCA § 303(4).

B

Tustumena Lake lies near the western edge of the Kenai Refuge and within the Kenai Wilderness. Tustumena Lake is the largest freshwater lake located within the Kenai Refuge and is the fifth largest freshwater lake in the State of Alaska. The lake’s outlet is the Kasilof River, which drains into the Cook Inlet, a tidal estuary that flows into the Gulf of Alaska and the Pacific Ocean.

As a result of its remote location, the ecosystem around and within Tustumena Lake is in a natural state. This ecosystem supports several species of anadromous fish, including sockeye salmon, which spawn within the Kasilof River watershed. A commercial fishing fleet, operating outside the boundaries of the Kenai Refuge, intercepts and harvests these sockeye salmon during their annual run from the Gulf of Alaska back to the Kasilof River, Tustumena Lake, and other spawning streams.

The antecedents of the present Enhancement Project date back to 1974, when the Alaska Department of Fish and Game (“ADF & G”) first conducted a sockeye salmon egg collection at Tustumena Lake as part of a research project designed to test the ability of the ecosystem to produce fish. The eggs were incubated at the Crooked Creek Hatchery, outside of the Kenai Refuge, and the resulting fry were stocked outside of the Kenai Refuge in the spring of 1975. In 1976, fry were first released into Tustumena Lake, and since have been released into Tustumena Lake in all but two subsequent years. The number of fry stocked yearly in Tustume-na Lake has ranged from a low of 400,000 in 1978 to a high of 17,050,000 in 1984. Since 1987, the number of fry released annually into the lake has been slightly greater than 6 million.

*1057 Before 1980, ADF & G operated the Enhancement Project without a special use permit, and ADF & G did not seek permits for the operation of the project. In 1980, following passage of ANILCA, the USFWS’s Refuge Manager for the Kenai Refuge notified ADF & G that special use permits would be required for all ongoing projects within the Refuge. In 1985, the USFWS and ADF &' G entered into a Memorandum of Understanding that allowed ADF & G annually to obtain a special use permit for the Enhancement Project to study the effect of stocking on native lake fish and on the incidence of disease within the fish population.

In 1989, the USFWS and ADF & G reached a joint agreement that by 1993 a decision should be made either to discontinue the research project at Tustumena Lake or to elevate it to enhance commercial fishing operations for the benefit of the Cook Inlet fishing industry. In a 1992 report, ADF & G requested that the project become an operational enhancement project. This report cited two reasons for conversion of the project. First, ADF & G concluded that the risk of adverse impacts on the Tustumena Lake ecosystem appeared to be lowered at a stocking rate of about 6 million fry per year. Second, ADF & G noted that, beginning in fiscal year 1992, a reduced state budget would require curtailing project evaluation. In 1993, ADF & G entered into a contract with the Cook Inlet Aquaculture Association (“CIAA”) to staff and run the Crooked Creek Hatchery and its hatchery programs.

The CIAA is a private, non-profit corporation “comprised of associations representative of commercial fishermen in the region” as well as “other user groups interested in fisheries within the region.” Alaska Stat. § 16.10.380(a) (2003). According to the USFWS’s final Environmental Assessment of the Enhancement Project, the CIAA is “organized for the purpose of engaging in salmon enhancement work throughout the Cook Inlet. Region.” The mission statement of the CIAA, according to the Environmental Assessment, is to:

,(1) protect self-perpetuating salmon stocks and the habitat upon which they depend; (2) rehabilitate self-perpetuating salmon stocks; (3) rehabilitate salmon habitat and (4) maximize the value of the Cook Inlet ... common property salmon resources by applying science and enhancement technology to supplement the value attained from protection and habitat rehabilitation of self-perpetuating salmon stocks.

The CIAA relies on funding from two sources. First, the Cook Inlet commercial salmon industry imposes a voluntary two percent tax on the value of its fishermen’s annual salmon harvest. Second, the CIAA generates income through producing hatchery-raised salmon from the surplus fry not used to stock Tustumena Lake.

In May 1994, the USFWS’s Regional Director contacted ADF & G in order to implement an evaluation of the Enhancement Project’s status and its future. Acknowledging that the Enhancement Project was initiated as an experimental project with the purpose of “supplementing] the commercial sockeye salmon fishery in the Cook Inlet,” the Regional Director set forth environmental concerns regarding the project and recommended that the Enhancement Project be evaluated through the National Environmental Policy Act (“NEPA”) review process. Among the .concerns raised were that the Enhancement Project potentially violated “the intent and purpose of the Wilderness Act, ANILCA, and regional policy,” and that the project would threaten “a unique, glacial, natural freshwater spawning and rearing ■ aquatic ecosystem .... merely to provide additional *1058 economic benefit primarily for Cook Inlet east side net fishermen.”

In late 1995, the CIAA submitted a draft Environmental Assessment (“EA”) to the USFWS for comment and review. See 40 C.F.R. § 1506.5(b) (2003); 550 FW 1 § 2.5(E)(2002 draft). The draft assessment proposed consideration of five action alternatives, from a total elimination of the Enhancement Project to a tripling of the number of salmon fry stocked in Tustume-na Lake, and recommended that the Enhancement Project continue at the same scale, with an annual stocking of about six million fry. After circulation and agency comment on the 1995 draft, in June 1997 the USFWS and the CIAA jointly released a draft EA of the Enhancement Project, which addressed concerns regarding the project, but the USFWS in a separate document concluded that mitigation measures could minimize risks of the project. During the 45-day period for public comment and review, the Wilderness Society submitted comments challenging the legality of “any fisheries enhancement program in designated Wilderness for the purpose of providing for the stocking of commerce” and questioning the compatibility of the project with the area’s wilderness designation. In August 1997, the final EA of the Enhancement Project was released. In a simultaneously released “Mitigated Finding of No Significant Impact,” the USFWS concluded that “mitigative measures” contained in the Special Use Permit would minimize risks associated with the Enhancement Project, and that preparation of an Environmental Impact Statement was not required.

Also in August 1997, the Kenai Refuge Manager issued a Wilderness Act Consistency Review, addressing legal concerns regarding whether the Enhancement Project was consistent with the Wilderness Act’s mandate to preserve wilderness in its natural condition and whether the project was a prohibited commercial enterprise. Referring to a legal opinion prepared by the United States Department of Interior’s Regional Solicitor’s Office, which concluded that the Enhancement Project “does not have to contribute to achieving Refuge purposes but it may not significantly conflict with them,” the Kenai Refuge Manager, in the Consistency Review, dismissed concerns that the project altered natural conditions and was a commercial enterprise. The Kenai Refuge Manager concluded that the Enhancement Project was consistent with the Wilderness Act, which he viewed as a legislative compromise not reflecting absolute preservationist values. The Refuge Manager also suggested that, because the State of Alaska had previously administered the project, criticism that the Enhancement Project was a commercial enterprise raised “a distinction without a difference.” In August 1997, the Refuge Manager also released a Compatibility Determination, which concluded that the Enhancement Project “cannot ... be considered as supporting refuge purposes, but neither can it be found incompatible with them.”

After issuance of these documents, the USFWS on August 8, 1997, issued a Special Use Permit to the CIAA for the Enhancement Project. Under the terms of this permit, each summer the CIAA establishes a temporary camp within the Kenai Wilderness at the mouth of Bear Creek, which flows into Tustumena Lake, and catches about 10,000 returning sockeye salmon, which yield about 10 million eggs. These eggs are transported to a hatchery outside the Kenai Wilderness. 4 The following spring about six million salmon fry produced by the eggs are stocked and returned to the wilderness in Bear Creek.

*1059 II

The Administrative Procedure Act (“APA”) governs judicial review of agency action. 5 U.S.C. § 701 et seq. Under the APA, we may set aside formal agency action only if “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” Id. § 706(2)(A); Center for Biological Diversity v. Veneman, 335 F.3d 849, 853 (9th Cir.2003). 5

A

There is disagreement among the parties as to what level of deference, if any, we should accord the USFWS’s decision to permit the Enhancement Project. Defendant USFWS maintains that the case is controlled by Chevron U.S.A. Inc. v. Natural Resources Defense Council, 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984), and that USFWS decisions interpreting the Wilderness Act and Refuge Act must be given broad deference. Plaintiffs, on the other hand, argue that the challenged project offends the literal terms of the Wilderness Act by not preserving the designated wilderness area and by sanctioning a commercial enterprise within it. Responding to the defendant’s argument for Chevron deference, which was adopted by the district court, Plaintiffs rely on the Supreme Court’s clarification of Chevron in United States v. Mead Corp., 533 U.S. 218, 121 S.Ct. 2164, 150 L.Ed.2d 292 (2001), urging that the USFWS’s permitting decision is entitled at most to “respect” as set forth in Skidmore v. Swift & Co., 323 U.S. 134, 65 S.Ct. 161, 89 L.Ed. 124 (1944).

In Chevron, the Supreme Court set forth a two-step test for judicial review of administrative agency interpretations of federal law. Under the first step: “If the intent of Congress is clear, that is the end of the matter; for the court, as well as the agency, must give effect to the unambiguously expressed intent of Congress.” Chevron, 467 U.S. at 842-43, 104 S.Ct. 2778. Congressional intent may be determined by “traditional tools of statutory construction,” and if a court using these tools ascertains that Congress had a clear intent on the question at issue, that intent must be given effect as law. Id. at 843 n. 9, 104 S.Ct. 2778; see Defenders of Wildlife v. Browner, 191 F.3d 1159, 1164 (9th Cir.1999) (stating that questions of congressional intent “are still firmly within the province of the courts under Chev ron”). Conversely, at step two of Chevron, when applicable, we recognize that if a statute is silent or ambiguous with respect to the issue at hand, then the reviewing court must defer to the agency so long as “the agency’s answer is based on a permissible construction of the statute.” 467 U.S. at 843, 104 S.Ct. 2778. In such a case an agency’s interpretation of a statute will be permissible, unless “arbitrary, capricious, or manifestly contrary to the statute.” Id. at 844,104 S.Ct. 2778.

Chevron considered only formal notice- and-comment rule-making and did not state what other types of agency decisions should be given such deference. In Mead, the Supreme Court clarified that “administrative implementation of a particular statutory provision qualifies for Chevron deference when it appears that Congress delegated authority to the agency generally to make rules carrying the force of law, and that the agency interpretation claiming deference was promulgated in the exercise of that authority.” 533 U.S. at 226-27, 121 S.Ct. 2164 (emphasis added). 6 *1060 Mead also clarified the weight that a reviewing court should give to administrative decisions not meeting these standards. Quoting Skidmore, the Court held that the deference to be accorded to such decisions depends upon “the thoroughness evident in its consideration, the validity of its reasoning, its consistency with earlier and later pronouncements, and all those factors which give it power to persuade, if lacking power to control.” Mead, 533 U.S. at 228, 121 S.Ct. 2164(quoting Skid-more, 323 U.S. at 140, 65 S.Ct. 161).

With the Supreme Court’s precedents in mind, we adopt the following analysis: Under Chevron’s first-step test, we ask whether the Enhancement Project offends the plain meaning and manifest congressional intent of the Wilderness Act or the Refuge Act. If so, Congress’s intent must be enforced and that is the end of the matter. Conversely, if the statutory terms are ambiguous, then we must give Chevron deference only upon a conclusion that the USFWS’s statutory interpretation has the “force of law.” Otherwise, we give the USFWS’s view respect if persuasive based on the factors recited in Skidmore and endorsed in Mead.

B

Addressing the first step in the Chevron analysis, we ask “whether Congress has directly spoken to the precise question at issue.” 467 U.S. at 842, 104 S.Ct. 2778. “If a court, employing traditional tools of statutory construction, ascertains that Congress had an intention on the precise question at issue, that intention is the law and must be given effect.” Id. at 843 n. 9, 104 S.Ct. 2778.

Canons of statutory construction help give meaning to a statute’s words. We begin with the language of the statute. Gwaltney of Smithfield, Ltd. v. Chesapeake Bay Found., Inc., 484 U.S. 49, 56, 108 S.Ct. 376, 98 L.Ed.2d 306 (1987) (“It is well settled that the starting point for interpreting a statute is the language of the statute itself.”) (internal quotation marks and citation omitted); Assoc. to Protect Hammersley, Eld & Totten Inlets v. Taylor Res., Inc., 299 F.3d 1007, 1015 (9th Cir.2002). Another fundamental canon of construction provides that “unless otherwise defined, words will be interpreted as taking their ordinary, contemporary, common meaning.” United States v. Smith, 155 F.3d 1051, 1057 (9th Cir.1998) (quoting Perrin v. United States, 444 U.S. 37, 42, 100 S.Ct. 311, 62 L.Ed.2d 199 (1979)); United States v. Iverson, 162 F.3d 1015, 1022 (9th Cir.1998).

It is also “a fundamental canon that the words of a statute must be read in their context and with a view to their place in the overall statutory scheme.” FDA v. Brown & Williamson Tobacco Corp., 529 U.S. 120, 133, 120 S.Ct. 1291, 146 L.Ed.2d 121 (2000) (quoting Davis v. Michigan Dep’t of Treasury, 489 U.S. 803, 809, 109 S.Ct. 1500, 103 L.Ed.2d 891 (1989)). If necessary to discern Congress’s intent, we may read statutory terms in light of the purpose of the statute. Thus, the structure and purpose of a- statute may also provide guidance in determining the plain meaning of its provisions. See K Mart Corp. v. Cartier, Inc., 486 U.S. 281, 291, 108 S.Ct. 1811, 100 L.Ed.2d 313 (1988) (“In ascertaining the plain meaning of [a] statute, the court must look to the particular *1061 statutory language at issue, as well as the language and design of the statute as a whole.”); United States v. Lewis, 67 F.3d 225, 228-29 (9th Cir.1995) (“Particular phrases must be construed in light of the overall purpose and structure of the whole statutory scheme.”). If, under these canons, or other traditional means of determining Congress’s intentions, we are able to determine that Congress spoke clearly to preclude the Enhancement Project, then we may not defer to the USFWS’s contrary interpretation. Medtronic, Inc. v. Lohr, 518 U.S. 470, 512, 116 S.Ct. 2240, 135 L.Ed.2d 700 (1996) (“Where the language of the statute is clear, resort to the agency’s interpretation is improper.”).

With these principles in mind, we assess Plaintiffs’ contention that the Enhancement Project offends the Wilderness Act. Most pertinent to our analysis is the Wilderness Act’s prohibition of commercial enterprise within designated wilderness. Section 4(c) of the Wilderness Act states that, subject to exceptions not relevant here, “there shall be no commercial enterprise ... within any wilderness area.” 16 U.S.C. § 1133(c). The Wilderness Act does not define the terms “commercial enterprise” or “within.” The district court considered these terms ambiguous and concluded that they do not bar the Enhancement Project.

Because no statutory or regulatory provision expressly defines the meaning of the term “commercial enterprise” as used in the Wilderness Act, we first consider the common sense meaning of the statute’s words to determine whether it is ambiguous. See Iverson, 162 F.3d at 1022. Webster’s defines “enterprise” to mean “a project or undertaking.” Webster’s Ninth New Collegiate Dictionary 415 (1985). Webster’s defines “commercial” as “occupied with or engaged in commerce or work intended for commerce; of or relating to commerce.” Id at 264-65. The American Heritage Dictionary of the English Language provides a strikingly similar definition, viewing “commercial” as meaning “l.a. of or relating to commerce, b. engaged in commerce, c. involved in work that is intended for the mass market.” American Heritage Dictionary of the English Language 371 (4th ed.2000). Black’s Law Dictionary adds that “commercial” may be defined as “relates to or is connected with trade and traffic or commerce in general; is occupied with business or commerce.” Black’s Law Dictionary 270 (6th ed.1990). These definitions suggest that a commercial enterprise is a project or undertaking of or relating to commerce.

We also consider the purposes of the Wilderness Act. The Act’s declaration of policy states as a goal the “preservation and protection” of wilderness lands “in their natural condition,” so as to “leave them unimpaired for future use and enjoyment as wilderness and so as to provide for the protection of these areas, [and] the preservation of their wilderness character.” 16 U.S.C. § 1131(a). The Wilderness Act further defines “wilderness,” in part, as “an area where the earth and its community of life are untrammeled by man.” Id. § 1131(c). These statutory declarations show a mandate of preservation for wilderness and the essential need to keep commerce out of it. Whatever else may be said about the positive aims of the Enhancement Project, it was not designed to advance the purposes of the Wilderness Act. The Enhancement Project to a degree places the goals and activities of commercial enterprise in the protected wilderness. The Enhancement Project is literally a project relating to commerce.

The structure of the relevant provisions of the Wilderness Act may also be considered. The Wilderness Act’s opening section first sets forth the Act’s broad mandate to protect the forests, waters and *1062 creatures of the wilderness in their natural, untrammeled state. 16 U.S.C. § 1131. Section 1133, devoted to the use of wilderness areas, contains a subsection entitled “[prohibition provisions.” Id. § 1133(c). Among these provisions is a broad prohibition on the operation of all commercial enterprise within a designated wilderness, except as “specifically provided for in this Act.” Id. The following subsection of the Act enumerates “special provisions,” including exceptions to this prohibition. Id. § 1133(d). This statutory structure, with prohibitions including an express bar on commercial enterprise within wilderness, limited by specific and express exceptions, shows a clear congressional intent generally to enforce the prohibition against “commercial enterprise” when the specified exceptions are not present. See United States v. Smith, 499 U.S. 160, 167, 111 S.Ct. 1180, 113 L.Ed.2d 134 (1991) (“Where Congress explicitly enumerates certain exceptions to a general prohibition, additional exceptions are not to be implied, in the absence of evidence of a contrary legislative intent.”) (quoting Andrus v. Glover Constr. Co., 446 U.S. 608, 616-17, 100 S.Ct. 1905, 64 L.Ed.2d 548 (1980)); Far West Fed. Bank, S.B. v. Director, Office of Thrift Supervision, 951 F.2d 1093, 1097 (9th Cir.1991) (“[W]hen Congress explicitly enumerates exceptions to a general scheme, exceptions not explicitly made should not be implied, absent evidence of contrary legislative intent.”). There is no exception given for commercial enterprise in wilderness when it has benign purpose and minimally intrusive impact.

The language, purpose and structure of the Wilderness Act support the conclusion that Congress spoke clearly to preclude commercial enterprise in the designated wilderness, regardless of the form of commercial activity, and regardless of whether it is aimed at assisting the economy with minimal intrusion on wilderness values.

C

Because the aim of Congress in the Wilderness Act to prohibit commercial enterprise within designated wilderness is clear, we do not owe deference to the USFWS’s determination regarding the permissibility of the Enhancement Project if it is a commercial enterprise. Chevron, 467 U.S. at 842-43,104 S.Ct. 2778.

The district court grounded its decision in part on an assessment that the impact on wilderness of millions of fry unseen beneath the waters of Bear Creek and Tustumena Lake was not terribly intrusive on wilderness values and that the project would hardly be noticed by those visiting the wilderness. The district court also was impressed that the CIAA was a nonprofit entity, that the State of Alaska heavily regulated the Enhancement Project, and that commercial effects of the project generally occurred years after the collection of salmon eggs and later release of the fry and were realized by commercial fishermen who sought their catch outside the wilderness bounds.

We thus deal with an activity with a benign aim to enhance the catch of fishermen, with little visible detriment to wilderness, under the cooperative banner of a non-profit trade association and state regulators. Surely this fish-stocking program, whose antecedents were a state run research project, is nothing like building a McDonald’s restaurant or a Wal-Mart store on the shores of Tustumena Lake. Nor is it like conducting a commercial fishing operation within designated wilderness, which we have previously proscribed. See Alaska Wildlife Alliance v. Jensen, 108 F.3d 1065, 1069 (9th Cir.1997). Nor is the project like cutting timber, extracting minerals, or otherwise- exploiting wilderness resources in a way that is plainly destructive of their preservation.

Conversely, the challenged activities do not appear to be aimed at furthering the *1063 goals of the Wilderness Act. The project is not aimed at preserving a threatened salmon run. 7 Looked at most favorably, for the proponents of the fish-stocking project, it might be concluded that the project only negligibly alters the wild character of Tustumena Lake and is not incompatible with refuge values, though those issues are disputed. 8 And it might also be considered that, to the extent the project is a servant of commerce, it may pose a threat to the wild, even if it operates under the eye of state and federal regulators.

Before further addressing the reasoning of the district court, we acknowledge that none of our precedent, and no explicit guidance from the United States Supreme Court, has addressed how to assess “commercial enterprise” when faced with activities involving mixed purposes and effects. The lack of explicit guidance on this issue in part led the district court to defer to the agency action. Yet we have determined that Congress absolutely proscribed commercial enterprise in the wilderness, and it is a traditional judicial function to apply that prohibition to the precise facts here, to determine if the challenged project may continue consistent with the will of Congress. • •

In light of Congress’s language and manifest intent, we conclude that the most sensible rule of decision to resolve whether an activity within designated wilderness bounds should be characterized as a “commercial enterprise” turns on an assessment of the purpose and effect of the activity. See Sierra Club v. Lyng, 662 F.Supp. 40, 42-43 (D.D.C.1987); see also Jensen, 108 F.3d at 1069 (9th Cir.1997). Lyng, though it involves a different issue under the Wilderness Act, is instructive on the issue of whether the Enhancement Project should be considered a commercial enterprise. In Lyng, plaintiffs challenged the legality of a United States Forest Service program to control pine beetle infestations in designated wilderness areas by an extensive tree-cutting and chemical-spraying campaign. Defendant urged that the eradication program was permissible, without justification, under section 4(d)(1) of the Wilderness Act, 16 U.S.C. § 1133(d)(1), under which the Secretary of Agriculture may take “such measures ... as may be necessary in the ■ control of fire, insects, and diseases,” within the designated wilderness. Rejecting this contention, the district court stressed that the “purpose and effect of the program [was] solely to protect commercial timber interests and private property,” and imposed an affirmative burden on the Secretary of Agriculture to justify the eradication program in light of wilderness values. Lyng, 662 F.Supp. at'42-43. 9

*1064 The consideration of purpose and effect of challenged actions not infrequently