Gonzales v. Carhart

delivered the opinion of the Court.

These cases require us to consider the validity of the Partial-Birth Abortion Ban Act of 2003 (Act), 18 U. S. C. § 1531 (2000 ed., Supp. IV), a federal statute regulating abortion procedures. In recitations preceding its operative provisions the Act refers to the Court’s opinion in Stenberg v. *133Carhart, 530 U. S. 914 (2000), which also addressed the subject of abortion procedures used in the later stages of pregnancy. Compared to the state statute at issue in Stenberg, the Act is more specific concerning the instances to which it applies and in this respect more precise in its coverage. We conclude the Act should be sustained against the objections lodged by the broad, facial attack brought against it.

In No. 05-380 (Carhart) respondents are LeRoy Carhart, William G. Fitzhugh, William H. Knorr, and Jill L. Vibhakar, doctors who perform second-trimester abortions. These doctors filed their complaint against the Attorney General of the United States in the United States District Court for the District of Nebraska. They challenged the constitutionality of the Act and sought a permanent injunction against its enforcement. Carhart v. Ashcroft, 331 F. Supp. 2d 805 (2004). In 2004, after a 2-week trial, the District Court granted a permanent injunction that prohibited the Attorney General from enforcing the Act in all cases but those in which there was no dispute the fetus was viable. Id., at 1048. The Court of Appeals for the Eighth Circuit affirmed. 413 F. 3d 791 (2005). We granted certiorari. 546 U. S. 1169 (2006).

In No. 05-1382 (Planned Parenthood) respondents are Planned Parenthood Federation of America, Inc., Planned Parenthood Golden Gate, and the City and County of San Francisco. The Planned Parenthood entities sought to enjoin enforcement of the Act in a suit filed in the United States District Court for the Northern District of California. Planned Parenthood Federation of Am. v. Ashcroft, 320 F. Supp. 2d 957 (2004). The City and County of San Francisco intervened as a plaintiff. In 2004, the District Court held a trial spanning a period just short of three weeks, and it, too, enjoined the Attorney General from enforcing the Act. Id., at 1035. The Court of Appeals for the Ninth Circuit affirmed. 435 F. 3d 1163 (2006). We granted certiorari. 547 U. S. 1205 (2006).

*134I

A

The Act proscribes a particular manner of ending fetal life, so it is necessary here, as it was in Stenberg, to discuss abortion procedures in some detail. Three United States District Courts heard extensive evidence describing the procedures. In addition to the two courts involved in the instant cases the District Court for the Southern District of New York also considered the constitutionality of the Act. National Abortion Federation v. Ashcroft, 330 F. Supp. 2d 436 (2004). It found the Act unconstitutional, id., at 493, and the Court of Appeals for the Second Circuit affirmed, National Abortion Federation v. Gonzales, 437 F. 3d 278 (2006). The three District Courts relied on similar medical evidence; indeed, much of the evidence submitted to the Carhart court previously had been submitted to the other two courts. 331 F. Supp. 2d, at 809-810. We refer to the District Courts’ exhaustive opinions in our own discussion of abortion procedures.

Abortion methods vary depending to some extent on the preferences of the physician and, of course, on the term of the pregnancy and the resulting stage of the unborn child’s development. Between 85 and 90 percent of the approximately 1.3 million abortions performed each year in the United States take place in the first three months of pregnancy, which is to say in the first trimester. Planned Parenthood, supra, at 960, and n. 4; App. in No. 05-1382, pp. 45-48. The most common first-trimester abortion method is vacuum aspiration (otherwise known as suction curettage) in which the physician vacuums out the embryonic tissue. Early in this trimester an alternative is to use medication, such as mifepristone (commonly known as RU-486), to terminate the pregnancy. National Abortion Federation, supra, at 464, n. 20. The Act does not regulate these procedures.

*135Of the remaining abortions that take place each year, most occur in the second trimester. The surgical procedure referred to as “dilation and evacuation” or “D&E” is the usual abortion method in this trimester. Planned Parenthood, supra, at 960-961. Although individual techniques for performing D&E differ, the general steps are the same.

A doctor must first dilate the cervix at least to the extent needed to insert surgical instruments into the uterus and to maneuver them to evacuate the fetus. National Abortion Federation, supra, at 465; App. in No. 05-1382, at 61. The steps taken to cause dilation differ by physician and gestational age of the fetus. See, e. g., Carhart, supra, at 852, 856, 859, 862-865, 868, 870, 873-874, 876-877, 880, 883, 886. A doctor often begins the dilation process by inserting osmotic dilators, such as laminaria (sticks of seaweed), into the cervix. The dilators can be used in combination with drugs, such as misoprostol, that increase dilation. The resulting amount of dilation is not uniform, and a doctor does not know in advance how an individual patient will respond. In general the longer dilators remain in the cervix, the more it will dilate. Yet the length of time doctors employ osmotic dilators varies. Some may keep dilators in the cervix for two days, while others use dilators for a day or less. National Abortion Federation, supra, at 464-465; Planned Parenthood, supra, at 961.

After sufficient dilation the surgical operation can commence. The woman is placed under general anesthesia or conscious sedation. The doctor, often guided by ultrasound, inserts grasping forceps through the woman’s cervix and into the uterus to grab the fetus. The doctor grips a fetal part with the forceps and pulls it back through the cervix and vagina, continuing to pull even after meeting resistance from the cervix. The friction causes the fetus to tear apart. For example, a leg might be ripped off the fetus as it is pulled through the cervix and out of the woman. The process of *136evacuating the fetus piece by piece continues until it has been completely removed. A doctor may make 10 to 15 passes with the forceps to evacuate the fetus in its entirety, though sometimes removal is completed with fewer passes. Once the fetus has been evacuated, the placenta and any remaining fetal material are suctioned or scraped out of the uterus. The doctor examines the different parts to ensure the entire fetal body has been removed. See, e. g., National Abortion Federation, supra, at 465; Planned Parenthood, 320 F. Supp. 2d, at 962.

Some doctors, especially later in the second trimester, may kill the fetus a day or two before performing the surgical evacuation. They inject digoxin or potassium chloride into the fetus, the umbilical cord, or the amniotic fluid. Fetal demise may cause contractions and make greater dilation possible. Once dead, moreover, the fetus’ body will soften, and its removal will be easier. Other doctors refrain from injecting chemical agents, believing it adds risk with little or no medical benefit. Carhart, supra, at 907-912; National Abortion Federation, supra, at 474-475.

The abortion procedure that was the impetus for the numerous bans on “partial-birth abortion,” including the Act, is a variation of this standard D&E. See M. Haskell, Dilation and Extraction for Late Second Trimester Abortion (1992), 1 Appellant’s App. in No. 04-3379 (CA8), p. 109 (hereinafter Dilation and Extraction). The medical community has not reached unanimity on the appropriate name for this D&E variation. It has been referred to as “intact D&E,” “dilation and extraction” (D&X), and “intact D&X.” National Abortion Federation, supra, at 440, n. 2; see also F. Cunningham et al., Williams Obstetrics 243 (22d ed. 2005) (identifying the procedure as D&X); Danforth’s Obstetrics and Gynecology 567 (J. Scott, R. Gibbs, B. Karlan, & A. Haney eds. 9th ed. 2003) (identifying the procedure as intact D&X); M. Paul, E. Lichtenberg, L. Borgatta, D. Grimes, & P. Stubblefield, A Clinician’s Guide to Medical and Surgical *137Abortion 136 (1999) (identifying the procedure as intact D&E). For discussion purposes this D&E variation will be referred to as intact D&E. The main difference between the two procedures is that in intact D&E a doctor extracts the fetus intact or largely intact with only a few passes. There are no comprehensive statistics indicating what percentage of all D&Es are performed in this manner.

Intact D&E, like regular D&E, begins with dilation of the cervix. Sufficient dilation is essential for the procedure. To achieve intact extraction some doctors thus may attempt to dilate the cervix to a greater degree. This approach has been called “serial” dilation. Carhart, 331 F. Supp. 2d, at 856, 870, 873; Planned Parenthood, supra, at 965. Doctors who attempt at the outset to perform intact D&E may dilate for two full days or use up to 25 osmotic dilators. See, e. g., Dilation and Extraction 110; Carhart, supra, at 865, 868, 876, 886.

In an intact D&E procedure the doctor extracts the fetus in a way conducive to pulling out its entire body, instead of ripping it apart. One doctor, for example, testified:

“If I know I have good dilation and I reach in and the fetus starts to come out and I think I can accomplish it, the abortion with an intact delivery, then I use my forceps a little bit differently. I don’t close them quite so much, and I just gently draw the tissue out attempting to have an intact delivery, if possible.” App. in No. 05-1382, at 74.

Rotating the fetus as it is being pulled decreases the odds of dismemberment. Carhart, supra, at 868-869; App. in No. 05-380, pp. 40-41; 5 Appellant’s App. in No. 04-3379 (CA8), at 1469. A doctor also “may use forceps to grasp a fetal part, pull it down, and re-grasp the fetus at a higher level — sometimes using both his hand and a forceps — to exert traction to retrieve the fetus intact until the head is lodged in the [cervix].” Carhart, supra, at 886-887.

*138Intact D&E gained public notoriety when, in 1992, Dr. Martin Haskell gave a presentation describing his method of performing the operation. Dilation and Extraction 110-111. In the usual intact D&E the fetus’ head lodges in the cervix, and dilation is insufficient to allow it to pass. See, e. g., ibid,.; App. in No. 05-380, at 577; App. in No. 05-1382, at 74, 282. Haskell explained the next step as follows:

“ At this point, the right-handed surgeon slides the fingers of the left [hand] along the back of the fetus and “hooks” the shoulders of the fetus with the index and ring fingers (palm down).

“ ‘While maintaining this tension, lifting the cervix and applying traction to the shoulders with the fingers of the left hand, the surgeon takes a pair of blunt curved Metzenbaum scissors in the right hand. He carefully advances the tip, curved down, along the spine and under his middle finger until he feels it contact the base of the skull under the tip of his middle finger.

“ ‘[T]he surgeon then forces the scissors into the base of the skull or into the foramen magnum. Having safely entered the skull, he spreads the scissors to enlarge the opening.

“‘The surgeon removes the scissors and introduces a suction catheter into this hole and evacuates the skull contents. With the catheter still in place, he applies traction to the fetus, removing it completely from the patient.’ ” H. R. Rep. No. 108-58, p. 3 (2003).

This is an abortion doctor’s clinical description. Here is another description from a nurse who witnessed the same method performed on a 26-week fetus and who testified before the Senate Judiciary Committee:

“‘Dr. Haskell went in with forceps and grabbed the baby’s legs and pulled them down into the birth canal. Then he delivered the baby’s body and the arms — every*139thing but the head. The doctor kept the head right inside the uterus....

“ ‘The baby’s little fingers were clasping and unclasping, and his little feet were kicking. Then the doctor stuck the scissors in the back of his head, and the baby’s arms jerked out, like a startle reaction, like a flinch, like a baby does when he thinks he is going to fall.

“‘The doctor opened up the scissors, stuck a high-powered suction tube into the opening, and sucked the baby’s brains out. Now the baby went completely limp... .

“ ‘He cut the umbilical cord and delivered the placenta. He threw the baby in a pan, along with the placenta and the instruments he had just used.’” Ibid.

Dr. Haskell's approach is not the only method of killing the fetus once its head lodges in the cervix, and “the process has evolved” since his presentation. Planned Parenthood, 320 F. Supp. 2d, at 965. Another doctor, for example, squeezes the skull after it has been pierced “so that enough brain tissue exudes to allow the head to pass through.” App. in No. 05-380, at 41; see also Carhart, 331 F. Supp. 2d, at 866-867, 874. Still other physicians reach into the cervix with their forceps and crush the fetus’ skull. Id., at 858, 881. Others continue to pull the fetus out of the woman until it disarticulates at the neck, in effect decapitating it. These doctors then grasp the head with forceps, crush it, and remove it. Id., at 864, 878; see also Planned Parenthood, supra, at 965.

Some doctors performing an intact D&E attempt to remove the fetus without collapsing the skull. See Carhart, supra, at 866, 869. Yet one doctor would not allow delivery of a live fetus younger than 24 weeks because “the objective of [his] procedure is to perform an abortion,” not a birth. App. in No. 05-1382, at 408-409. The doctor thus answered in the affirmative when asked whether he would “hold the fetus’ head on the internal side of the [cervix] in order to *140collapse the skull” and kill the fetus before it is born. Id., at 409; see also Carhart, supra, at 862, 878. Another doctor testified he crushes a fetus’ skull not only to reduce its size but also to ensure the fetus is dead before it is removed. For the staff to have to deal with a fetus that has “some viability to it, some movement of limbs,” according to this doctor, “[is] always a difficult situation.” App. in No. 05-380, at 94; see Carhart, supra, at 858.

D&E and intact D&E are not the only second-trimester abortion methods. Doctors also may abort a fetus through medical induction. The doctor medicates the woman to induce labor, and contractions occur to deliver the fetus. Induction, which unlike D&E should occur in a hospital, can last as little as 6 hours but can take longer than 48. It accounts for about 5 percent of second-trimester abortions before 20 weeks of gestation and 15 percent of those after 20 weeks. Doctors turn to two other methods of second-trimester abortion, hysterotomy and hysterectomy, only in emergency situations because they carry increased risk of complications. In a hysterotomy, as in a cesarean section, the doctor removes the fetus by making an incision through the abdomen and uterine wall to gain access to the uterine cavity. A hysterectomy requires the removal of the entire uterus. These two procedures represent about 0.07 percent of second-trimester abortions. National Abortion Federation, 330 F. Supp. 2d, at 467; Planned Parenthood, supra, at 962-963.

B

After Dr. Haskell’s procedure received public attention, with ensuing and increasing public concern, bans on “ ‘partial birth abortion’ ” proliferated. By the time of the Stenberg decision, about 30 States had enacted bans designed to prohibit the procedure. 530 U. S., at 995-996, and nn. 12-13 (Thomas, J., dissenting); see also H. R. Rep. No. 108-58, at 4-5. In 1996, Congress also acted to ban partial-birth abortion. President Clinton vetoed the congressional legis*141lation, and the Senate failed to override the veto. Congress approved another bill banning the procedure in 1997, but President Clinton again vetoed it. In 2003, after this Court’s decision in Stenberg, Congress passed the Act at issue here. H. R. Rep. No. 108-58, at 12-14. On November 5, 2003, President Bush signed the Act into law. It was to take effect the following day. 18 U. S. C. § 1531(a) (2000 ed., Supp. IV).

The Act responded to Stenberg in two ways. First, Congress made factual findings. Congress determined that this Court in Stenberg “was required to accept the very questionable findings issued by the district court judge,” §2(7), 117 Stat. 1202, notes following 18 U. S. C. § 1531 (2000 ed., Supp. IV), p. 768, ¶ (7) (hereinafter Congressional Findings), but that Congress was “not bound to accept the same factual findings,” id., ¶ (8). Congress found, among other things, that “[a] moral, medical, and ethical consensus exists that the practice of performing a partial-birth abortion ... is a gruesome and inhumane procedure that is never medically necessary and should be prohibited.” Id., ¶ (1).

Second, and more relevant here, the Act’s language differs from that of the Nebraska statute struck down in Stenberg. See 530 U. S., at 921-922 (quoting Neb. Rev. Stat. Ann. §§28-328(1), 28-326(9) (Supp. 1999)). The operative provisions of the Act provide in relevant part:

“(a) Any physician who, in or affecting interstate or foreign commerce, knowingly performs a partial-birth abortion and thereby kills a human fetus shall be fined under this title or imprisoned not more than 2 years, or both. This subsection does not apply to a partial-birth abortion that is necessary to save the life of a mother whose life is endangered by a physical disorder, physical illness, or physical injury, including a life-endangering physical condition caused by or arising from the pregnancy itself. This subsection takes effect 1 day after the enactment.

*142“(b) As used in this section—

“(1) the term ‘partial-birth abortion’ means an abortion in which the person performing the abortion—

“(A) deliberately and intentionally vaginally delivers a living fetus until, in the case of a head-first presentation, the entire fetal head is outside the body of the mother, or, in the case of breech presentation, any part of the fetal trunk past the navel is outside the body of the mother, for the purpose of performing an overt act that the person knows will kill the partially delivered living fetus; and

“(B) performs the overt act, other than completion of delivery, that kills the partially delivered living fetus; and

“(2) the term ‘physician’ means a doctor of medicine or osteopathy legally authorized to practice medicine and surgery by the State in which the doctor performs such activity, or any other individual legally authorized by the State to perform abortions: Provided, however, That any individual who is not a physician or not otherwise legally authorized by the State to perform abortions, but who nevertheless directly performs a partial-birth abortion, shall be subject to the provisions of this section.

“(d)(1) A defendant accused of an offense under this section may seek a hearing before the State Medical Board on whether the physician’s conduct was necessary to save the life of the mother whose life was endangered by a physical disorder, physical illness, or physical injury, including a life-endangering physical condition caused by or arising from the pregnancy itself.

“(2) The findings on that issue are admissible on that issue at the trial of the defendant. Upon a motion of the defendant, the court shall delay the beginning of the *143trial for not more than 30 days to permit such a hearing to take place.

“(e) A woman upon whom a partial-birth abortion is performed may not be prosecuted under this section, for a conspiracy to violate this section, or for an offense under section 2, 3, or 4 of this title based on a violation of this section.” 18 U. S. C. § 1531 (2000 ed., Supp. IV).

The Act also includes a provision authorizing civil actions that is not of relevance here. § 1531(c).

C

The District Court in Carhart concluded the Act was unconstitutional for two reasons. First, it determined the Act was unconstitutional because it lacked an exception allowing the procedure where necessary for the health of the mother. 331 F. Supp. 2d, at 1004-1030. Second, the District Court found the Act deficient because it covered not merely intact D&E but also certain other D&Es. Id., at 1030-1037.

The Court of Appeals for the Eighth Circuit addressed only the lack of a health exception. 413 F. 3d, at 803-804. The court began its analysis with what it saw as the appropriate question — “whether ‘substantial medical authority’ supports the medical necessity of the banned procedure.” Id., at 796 (quoting Stenberg, supra, at 938). This was the proper framework, according to the Court of Appeals, because “when a lack of consensus exists in the medical community, the Constitution requires legislatures to err on the side of protecting women’s health by including a health exception.” 413 F. 3d, at 796. The court rejected the Attorney General’s attempt to demonstrate changed evidentiary circumstances since Stenberg and considered itself bound by Stenberg’s conclusion that a health exception was required. 413 F. 3d, at 803 (explaining “[t]he record in [the] case and the record in Stenberg [were] similar in all significant respects”). It invalidated the Act. Ibid.

*144D

The District Court in Planned Parenthood concluded the Act was unconstitutional “because it (1) pose[d] an undue burden on a woman’s ability to choose a second trimester abortion; (2) [was] unconstitutionally vague; and (3) required] a health exception as set forth by . . . Stenberg.” 320 F. Supp. 2d, at 1034-1035.

The Court of Appeals for the Ninth Circuit agreed. Like the Court of Appeals for the Eighth Circuit, it concluded the absence of a health exception rendered the Act unconstitutional. The court interpreted Stenberg to require a health exception unless “there is consensus in the medical community that the banned procedure is never medically necessary to preserve the health of women.” 435 F. 3d, at 1173. Even after applying a deferential standard of review to Congress’ factual findings, the Court of Appeals determined “substantial disagreement exists in the medical community regarding whether” the procedures prohibited by the Act are ever necessary to preserve a woman’s health. Id., at 1175-1176.

The Court of Appeals concluded further that the Act placed an undue burden on a woman’s ability to obtain a second-trimester abortion. The court found the textual differences between the Act and the Nebraska statute struck down in Stenberg insufficient to distinguish D&E and intact D&E. 435 F. 3d, at 1178-1180. As a result, according to the Court of Appeals, the Act imposed an undue burden because it prohibited D&E. Id., at 1180-1181.

Finally, the Court of Appeals found the Act void for vagueness. Id., at 1181. Abortion doctors testified they were uncertain which procedures the Act made criminal. The court thus concluded the Act did not offer physicians clear warning of its regulatory reach. Id., at 1181-1184. Resting on its understanding of the remedial framework established by this Court in Ayotte v. Planned Parenthood of Northern New Eng., 546 U. S. 320, 328-330 (2006), the Court of Appeals held *145the Act was unconstitutional on its face and should be permanently enjoined. 435 F. 3d, at 1184-1191.

II

The principles set forth in the joint opinion in Planned Parenthood of Southeastern Pa. v. Casey, 505 U. S. 833 (1992), did not find support from all those who join the instant opinion. See id., at 979-1002 (Scalia, J., joined by Thomas, J., inter alios, concurring in judgment in part and dissenting in part). Whatever one’s views concerning the Casey joint opinion, it is evident a premise central to its conclusion — that the government has a legitimate and substantial interest in preserving and promoting fetal life — would be repudiated were the Court now to affirm the judgments of the Courts of Appeals.

Casey involved a challenge to Roe v. Wade, 410 U. S. 113 (1973). The opinion contains this summary:

“It must be stated at the outset and with clarity that Roe’s essential holding, the holding we reaffirm, has three parts. First is a recognition of the right of the woman to choose to have an abortion before viability and to obtain it without undue interference from the State. Before viability, the State’s interests are not strong enough to support a prohibition of abortion or the imposition of a substantial obstacle to the woman’s effective right to elect the procedure. Second is a confirmation of the State’s power to restrict abortions after fetal viability, if the law contains exceptions for pregnancies which endanger the woman’s life or health. And third is the principle that the State has legitimate interests from the outset of the pregnancy in protecting the health of the woman and the life of the fetus that may become a child. These principles do not contradict one another; and we adhere to each.” 505 U. S., at 846 (opinion of the Court).

*146Though all three holdings are implicated in the instant cases, it is the third that requires the most extended discussion; for we must determine whether the Act furthers the legitimate interest of the Government in protecting the life of the fetus that may become a child.

To implement its holding, Casey rejected both Roe’s rigid trimester framework and the interpretation of Roe that considered all previability regulations of abortion unwarranted. 505 U. S., at 875-876, 878 (plurality opinion). On this point Casey overruled the holdings in two cases because they undervalued the State’s interest in potential life. See id., at 881-883 (joint opinion) (overruling Thornburgh v. American College of Obstetricians and Gynecologists, 476 U. S. 747 (1986), and Akron v. Akron Center for Reproductive Health, Inc., 462 U. S. 416 (1983)).

We assume the following principles for the purposes of this opinion. Before viability, a State “may not prohibit any woman from making the ultimate decision to terminate her pregnancy.” 505 U. S., at 879 (plurality opinion). It also may not impose upon this right an undue burden, which exists if a regulation’s “purpose or effect is to place a substantial obstacle in the path of a woman seeking an abortion before the fetus attains viability.” Id., at 878. On the other hand, “[regulations which do no more than create a structural mechanism by which the State, or the parent or guardian of a minor, may express profound respect for the life of the unborn are permitted, if they are not a substantial obstacle to the woman’s exercise of the right to choose.” Id., at 877. Casey, in short, struck a balance. The balance was central to its holding. We now apply its standard to the cases at bar.

Ill

We begin with a determination of the Act’s operation and effect. A straightforward reading of the Act’s text demonstrates its purpose and the scope of its provisions: It regu*147lates and proscribes, with exceptions or qualifications to be discussed, performing the intact D&E procedure.

Respondents agree the Act encompasses intact D&E, but they contend its additional reach is both unclear and excessive. . Respondents assert that, at the least, the Act is void for vagueness because its scope is indefinite. In the alternative, respondents argue the Act’s text proscribes all D&Es. Because D&E is the most common second-trimester abortion method, respondents suggest the Act imposes an undue burden. In this litigation the Attorney General does not dispute that the Act would impose an undue burden if it covered standard D&E.

We conclude that the Act is not void for vagueness, does not impose an undue burden from any overbreadth, and is not invalid on its face.

A

The Act punishes “knowingly performing] ” a “partial-birth abortion.” § 1531(a) (2000 ed., Supp. IV). It defines the unlawful abortion in explicit terms. § 1531(b)(1).

First, the person performing the abortion must “vaginally delivejr] a living fetus.” § 1531(b)(1)(A). The Act does not restrict an abortion procedure involving the delivery of an expired fetus. The Act, furthermore, is inapplicable to abortions that do not involve vaginal delivery (for instance, hysterotomy or hysterectomy). The Act does apply both previability and postviability because, by common understanding and scientific terminology, a fetus is a living organism while within the womb, whether or not it is viable outside the womb. See, e. g., Planned Parenthood, 320 F. Supp. 2d, at 971-972. We do not understand this point to be contested by the parties.

Second, the Act’s definition of partial-birth abortion requires the fetus to be delivered “until, in the case of a headfirst presentation, the entire fetal head is outside the body of the mother, or, in the case of breech presentation, any part *148of the fetal trunk past the navel is outside the body of the mother.” § 1531(b)(1)(A). The Attorney General concedes, and we agree, that if an abortion procedure does not involve the delivery of a living fetus to one of these “anatomical ‘landmarks’” — where, depending on the presentation, either the fetal head or the fetal trunk past the navel is outside the body of the mother — the prohibitions of the Act do not apply. Brief for Petitioner in No. 05-380, p. 46.

Third, to fall within the Act, a doctor must perform an “overt act, other than completion of delivery, that kills the partially delivered living fetus.” § 1531(b)(1)(B). For purposes of criminal liability, the overt act causing the fetus’ death must be separate from delivery. And the overt act must occur after the delivery to an anatomical landmark. This is because the Act proscribes killing “the partially delivered” fetus, which, when read in context, refers to a fetus that has been delivered to an anatomical landmark. Ibid.

Fourth, the Act contains scienter requirements concerning all the actions involved in the prohibited abortion. To begin with, the physician must have “deliberately and intentionally” delivered the fetus to one of the Act’s anatomical landmarks. § 1531(b)(1)(A). If a living fetus is delivered past the critical point by accident or inadvertence, the Act is inapplicable. In addition, the fetus must have been delivered “for the purpose of performing an overt act that the [doctor] knows will kill [it].” Ibid. If either intent is absent, no crime has occurred. This follows from the general principle that where scienter is required no crime is committed absent the requisite state of mind. See generally 1 W. LaFave, Substantive Criminal Law § 5.1 (2d ed. 2003) (hereinafter La-Fave); 1 C. Torcía, Wharton’s Criminal Law §27 (15th ed. 1993).

B

Respondents contend the language described above is indeterminate, and they thus argue the Act is unconstitutionally vague on its face. “As generally stated, the void-for-*149vagueness doctrine requires that a penal statute define the criminal offense with sufficient definiteness that ordinary people can understand what conduct is prohibited and in a manner that does not encourage arbitrary and discriminatory enforcement.” Kolender v. Lawson, 461 U. S. 352, 357 (1983); Posters ‘N’ Things, Ltd. v. United States, 511 U. S. 513, 525 (1994). The Act satisfies both requirements.

The Act provides doctors “of ordinary intelligence a reasonable opportunity to know what is prohibited.” Grayned v. City of Rockford, 408 U. S. 104,108 (1972). Indeed, it sets forth “relatively clear guidelines as to prohibited conduct” and provides “objective criteria” to evaluate whether a doctor has performed a prohibited procedure. Posters ‘N’ Things, supra, at 525-526. Unlike the statutory language in Stenberg that prohibited the delivery of a “‘substantial portion’ ” of the fetus — where a doctor might question how much of the fetus is a substantial portion — the Act defines the line between potentially criminal conduct on the one hand and lawful abortion on the other. Stenberg, 530 U. S., at 922 (quoting Neb. Rev. Stat. Ann. §28-326(9) (Supp. 1999)). Doctors performing D&E will know that if they do not deliver a living fetus to an anatomical landmark they will not face criminal liability.

This conclusion is buttressed by the intent that must be proved to impose liability. The Court has made clear that scienter requirements alleviate vagueness concerns. Posters ‘N’ Things, supra, at 526; see also Colautti v. Franklin, 439 U. S. 379, 395 (1979) (“This Court has long recognized that the constitutionality of a vague statutory standard is closely related to whether that standard incorporates a requirement of mens rea”). The Act requires the doctor deliberately to have delivered the fetus to an anatomical landmark. 18 U.S.C. § 1531(b)(1)(A) (2000 ed., Supp. IV). Because a doctor performing a D&E will not face criminal liability if he or she delivers a fetus beyond the prohibited point by mistake, the Act cannot be described as “a trap for *150those who act in good faith.” Colautti, supra, at 395 (internal quotation marks omitted).

Respondents likewise have failed to show that the Act should be invalidated on its face because it encourages arbitrary or discriminatory enforcement.