In each of these cases, a 14-year-old was convicted of murder and sentenced to a mandatory term of life imprisonment without the possibility of parole. In No. 10−9647, petitioner Jackson accompanied two other boys to a video store to commit a robbery; on the way to the store, he learned that one of the boys was carrying a shotgun. Jackson stayed outside the store for most of the robbery, but after he entered, one of his co-conspirators shot and killed the store clerk. Arkansas charged Jackson as an adult with capital felony murder and aggravated robbery, and a jury convicted him of both crimes. The trial court imposed a statutorily mandated sentence of life imprisonment without the possibility of parole. Jackson filed a state habeas petition, arguing that a mandatory life-without-parole term for a 14-year-old violates the Eighth Amendment. Disagreeing, the court granted the State’s motion to dismiss. The Arkansas Supreme Court affirmed.

In No. 10−9646, petitioner Miller, along with a friend, beat Miller’s neighbor and set fire to his trailer after an evening of drinking and drug use. The neighbor died. Miller was initially charged as a juvenile, but his case was removed to adult court, where he was charged with murder in the course of arson. A jury found Miller guilty, and the trial court imposed a statutorily mandated punishment of life without parole. The Alabama Court of Criminal Appeals affirmed, holding that Miller’s sentence was not overly harsh when compared to his crime, and that its mandatory nature was permissible under the Eighth Amendment.

Held: The Eighth Amendment forbids a sentencing scheme that mandates life in prison without possibility of parole for juvenile homicide offenders. Pp. 6−27.

(a) The Eighth Amendment’s prohibition of cruel and unusual punishment “guarantees individuals the right not to be subjected to excessive sanctions.” Roper v. Simmons, 543 U. S. 551. That right “flows from the basic ‘precept of justice that punishment for crime should be graduated and proportioned’ ” to both the offender and the offense. Ibid.

Two strands of precedent reflecting the concern with proportionate punishment come together here. The first has adopted categorical bans on sentencing practices based on mismatches between the culpability of a class of offenders and the severity of a penalty. See, e.g., Kennedy v. Louisiana, 554 U. S. 407. Several cases in this group have specially focused on juvenile offenders, because of their lesser culpability. Thus, Roper v. Simmons held that the Eighth Amendment bars capital punishment for children, and Graham v. Florida, 560 U. S. ___, concluded that the Amendment prohibits a sentence of life without the possibility of parole for a juvenile convicted of a nonhomicide offense. Graham further likened life without parole for juveniles to the death penalty, thereby evoking a second line of cases. In those decisions, this Court has required sentencing authorities to consider the characteristics of a defendant and the details of his offense before sentencing him to death. See, e.g., Woodson v. North Carolina, 428 U. S. 280 (plurality opinion). Here, the confluence of these two lines of precedent leads to the conclusion that mandatory life without parole for juveniles violates the Eighth Amendment.

As to the first set of cases: Roper and Graham establish that children are constitutionally different from adults for sentencing purposes. Their “ ‘lack of maturity’ ” and “ ‘underdeveloped sense of responsibility’ ” lead to recklessness, impulsivity, and heedless risk-taking. Roper, 543 U. S., at 569. They “are more vulnerable . . . to negative influences and outside pressures,” including from their family and peers; they have limited “contro[l] over their own environment” and lack the ability to extricate themselves from horrific, crime-producing settings. Ibid. And because a child’s character is not as “well formed” as an adult’s, his traits are “less fixed” and his actions are less likely to be “evidence of irretrievabl[e] deprav[ity].” Id., at 570. Roper and Graham emphasized that the distinctive attributes of youth diminish the penological justifications for imposing the harshest sentences on juvenile offenders, even when they commit terrible crimes.

While Graham’s flat ban on life without parole was for nonhomicide crimes, nothing that Graham said about children is crime-specific. Thus, its reasoning implicates any life-without-parole sentence for a juvenile, even as its categorical bar relates only to nonhomicide offenses. Most fundamentally, Graham insists that youth matters in determining the appropriateness of a lifetime of incarceration without the possibility of parole. The mandatory penalty schemes at issue here, however, prevent the sentencer from considering youth and from assessing whether the law’s harshest term of imprisonment proportionately punishes a juvenile offender. This contravenes Graham’s (and also Roper’s) foundational principle: that imposition of a State’s most severe penalties on juvenile offenders cannot proceed as though they were not children.

Graham also likened life-without-parole sentences for juveniles to the death penalty. That decision recognized that life-without-parole sentences “share some characteristics with death sentences that are shared by no other sentences.” 560 U. S., at ___. And it treated life without parole for juveniles like this Court’s cases treat the death penalty, imposing a categorical bar on its imposition for nonhomicide offenses. By likening life-without-parole sentences for juveniles to the death penalty, Graham makes relevant this Court’s cases demanding individualized sentencing in capital cases. In particular, those cases have emphasized that sentencers must be able to consider the mitigating qualities of youth. In light of Graham’s reasoning, these decisions also show the flaws of imposing mandatory life-without-parole sentences on juvenile homicide offenders. Pp. 6−17.

(b) The counterarguments of Alabama and Arkansas are unpersuasive. Pp. 18–27. (1) The States first contend that Harmelin v. Michigan, 501 U. S. 957, forecloses a holding that mandatory life-without-parole sentences for juveniles violate the Eighth Amendment. Harmelin declined to extend the individualized sentencing requirement to noncapital cases “because of the qualitative difference between death and all other penalties.” Id., at 1006 (Kennedy, J., concurring in part and concurring in judgment). But Harmelin had nothing to do with children, and did not purport to apply to juvenile offenders. Indeed, since Harmelin, this Court has held on multiple occasions that sentencing practices that are permissible for adults may not be so for children. See Roper, 543 U. S. 551; Graham, 560 U. S ___.

The States next contend that mandatory life-without-parole terms for juveniles cannot be unconstitutional because 29 jurisdictions impose them on at least some children convicted of murder. In considering categorical bars to the death penalty and life without parole, this Court asks as part of the analysis whether legislative enactments and actual sentencing practices show a national consensus against a sentence for a particular class of offenders. But where, as here, this Court does not categorically bar a penalty, but instead requires only that a sentencer follow a certain process, this Court has not scrutinized or relied on legislative enactments in the same way. See, e.g., Sumner v. Schuman, 483 U. S. 66.

In any event, the “objective indicia of society’s standards,” Graham, 560 U. S., at ___, that the States offer do not distinguish these cases from others holding that a sentencing practice violates the Eighth Amendment. Fewer States impose mandatory life-without-parole sentences on juvenile homicide offenders than authorized the penalty (life-without-parole for nonhomicide offenders) that this Court invalidated in Graham. And as Graham and Thompson v. Oklahoma, 487 U. S. 815, explain, simply counting legislative enactments can present a distorted view. In those cases, as here, the relevant penalty applied to juveniles based on two separate provisions: One allowed the transfer of certain juvenile offenders to adult court, while another set out penalties for any and all individuals tried there. In those circumstances, this Court reasoned, it was impossible to say whether a legislature had endorsed a given penalty for children (or would do so if presented with the choice). The same is true here. Pp. 18–25.

(2) The States next argue that courts and prosecutors sufficiently consider a juvenile defendant’s age, as well as his background and the circumstances of his crime, when deciding whether to try him as an adult. But this argument ignores that many States use mandatory transfer systems. In addition, some lodge the decision in the hands of the prosecutors, rather than courts. And even where judges have transfer-stage discretion, it has limited utility, because the decisionmaker typically will have only partial information about the child or the circumstances of his offense. Finally, because of the limited sentencing options in some juvenile courts, the transfer decision may present a choice between a light sentence as a juvenile and standard sentencing as an adult. It cannot substitute for discretion at post-trial sentencing. Pp. 25−27.

No. 10−9646, 63 So. 3d 676, and No. 10−9647, 2011 Ark. 49, ___ S. W. 3d ___, reversed and remanded.

Kagan, J., delivered the opinion of the Court, in which Kennedy, Ginsburg, Breyer, and Sotomayor, JJ., joined. Breyer, J., filed a concurring opinion, in which Sotomayor, J., joined. Roberts, C. J., filed a dissenting opinion, in which Scalia, Thomas, and Alito, JJ., joined. Thomas, J., filed a dissenting opinion, in which Scalia, J., joined. Alito, J., filed a dissenting opinion, in which Scalia, J., joined.

NOTES

1 Together with No. 10–9647, Jackson v. Hobbs, Director, Arkansas Department of Correction, on certiorari to the Supreme Court of Arkansas.

An Arizona statute known as S. B. 1070 was enacted in 2010 to address pressing issues related to the large number of unlawful aliens in the State. The United States sought to enjoin the law as preempted. The District Court issued a preliminary injunction preventing four of its provisions from taking effect. Section 3 makes failure to comply with federal alien-registration requirements a state misdemeanor; §5(C) makes it a misdemeanor for an unauthorized alien to seek or engage in work in the State; §6 authorizes state and local officers to arrest without a warrant a person “the officer has probable cause to believe . . . has committed any public offense that makes the person removable from the United States”; and §2(B) requires officers conducting a stop, detention, or arrest to make efforts, in some circumstances, to verify the person’s immigration status with the Federal Government. The Ninth Circuit affirmed, agreeing that the United States had established a likelihood of success on its preemption claims.

Held:

1. The Federal Government’s broad, undoubted power over immigration and alien status rests, in part, on its constitutional power to “establish an uniform Rule of Naturalization,” Art. I, §8, cl. 4, and on its inherent sovereign power to control and conduct foreign relations, see Toll v. Moreno, 458 U. S. 1. Federal governance is extensive and complex. Among other things, federal law specifies categories of aliens who are ineligible to be admitted to the United States, 8 U. S. C. §1182; requires aliens to register with the Federal Government and to carry proof of status, §§1304(e), 1306(a); imposes sanctions on employers who hire unauthorized workers, §1324a; and specifies which aliens may be removed and the procedures for doing so, see §1227. Removal is a civil matter, and one of its principal features is the broad discretion exercised by immigration officials, who must decide whether to pursue removal at all. Immigration and Customs Enforcement (ICE), an agency within the Department of Homeland Security, is responsible for identifying, apprehending, and removing illegal aliens. It also operates the Law Enforcement Support Center, which provides immigration status information to federal, state, and local officials around the clock. Pp. 2–7.

2. The Supremacy Clause gives Congress the power to preempt state law. A statute may contain an express preemption provision, see, e.g., Chamber of Commerce of United States of America v. Whiting, 563 U. S. ___, ___, but state law must also give way to federal law in at least two other circumstances. First, States are precluded from regulating conduct in a field that Congress has determined must be regulated by its exclusive governance. See Gade v. National Solid Wastes Management Assn., 505 U. S. 88. Intent can be inferred from a framework of regulation “so pervasive . . . that Congress left no room for the States to supplement it” or where a “federal interest is so dominant that the federal system will be assumed to preclude enforcement of state laws on the same subject.” Rice v. Santa Fe Elevator Corp., 331 U. S. 218. Second, state laws are preempted when they conflict with federal law, including when they stand “as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress.” Hines v. Davidowitz, 312 U. S. 52. Pp. 7–8.

3. Sections 3, 5(C), and 6 of S. B. 1070 are preempted by federal law. Pp. 8–19.

(a) Section 3 intrudes on the field of alien registration, a field in which Congress has left no room for States to regulate. In Hines, a state alien-registration program was struck down on the ground that Congress intended its “complete” federal registration plan to be a “single integrated and all-embracing system.” 312 U. S., at 74. That scheme did not allow the States to “curtail or complement” federal law or “enforce additional or auxiliary regulations.” Id., at 66–67. The federal registration framework remains comprehensive. Because Congress has occupied the field, even complementary state regulation is impermissible. Pp. 8–11.

(b) Section 5(C)’s criminal penalty stands as an obstacle to the federal regulatory system. The Immigration Reform and Control Act of 1986 (IRCA), a comprehensive framework for “combating the employment of illegal aliens,” Hoffman Plastic Compounds, Inc. v. NLRB, 535 U. S. 137, makes it illegal for employers to knowingly hire, recruit, refer, or continue to employ unauthorized workers, 8 U. S. C. §§1324a(a)(1)(A), (a)(2), and requires employers to verify prospective employees’ employment authorization status, §§1324a(a)(1)(B), (b). It imposes criminal and civil penalties on employers, §§1324a(e)(4), (f), but only civil penalties on aliens who seek, or engage in, unauthorized employment, e.g., §§1255(c)(2), (c)(8). IRCA’s express preemption provision, though silent about whether additional penalties may be imposed against employees, “does not bar the ordinary working of conflict pre-emption principles” or impose a “special burden” making it more difficult to establish the preemption of laws falling outside the clause. Geier v. American Honda Motor Co., 529 U. S. 861–872. The correct instruction to draw from the text, structure, and history of IRCA is that Congress decided it would be inappropriate to impose criminal penalties on unauthorized employees. It follows that a state law to the contrary is an obstacle to the regulatory system Congress chose. Pp. 12–15.

(c) By authorizing state and local officers to make warrantless arrests of certain aliens suspected of being removable, §6 too creates an obstacle to federal law. As a general rule, it is not a crime for a removable alien to remain in the United States. The federal scheme instructs when it is appropriate to arrest an alien during the removal process. The Attorney General in some circumstances will issue a warrant for trained federal immigration officers to execute. If no federal warrant has been issued, these officers have more limited authority. They may arrest an alien for being “in the United States in violation of any [immigration] law or regulation,” for example, but only where the alien “is likely to escape before a warrant can be obtained.” §1357(a)(2). Section 6 attempts to provide state officers with even greater arrest authority, which they could exercise with no instruction from the Federal Government. This is not the system Congress created. Federal law specifies limited circumstances in which state officers may perform an immigration officer’s functions. This includes instances where the Attorney General has granted that authority in a formal agreement with a state or local government. See, e.g., §1357(g)(1). Although federal law permits state officers to “cooperate with the Attorney General in the identification, apprehension, detention, or removal of aliens not lawfully present in the United States,” §1357(g)(10)(B), this does not encompass the unilateral decision to detain authorized by §6. Pp. 15–19.

4. It was improper to enjoin §2(B) before the state courts had an opportunity to construe it and without some showing that §2(B)’s enforcement in fact conflicts with federal immigration law and its objectives. Pp. 19–24.

(a) The state provision has three limitations: A detainee is presumed not to be an illegal alien if he or she provides a valid Arizona driver’s license or similar identification; officers may not consider race, color, or national origin “except to the extent permitted by the United States [and] Arizona Constitution[s]”; and §2(B) must be “implemented in a manner consistent with federal law regulating immigration, protecting the civil rights of all persons and respecting the privileges and immunities of United States citizens.” P. 20.

(b) This Court finds unpersuasive the argument that, even with those limits, §2(B) must be held preempted at this stage. Pp. 20–24.

(1) The mandatory nature of the status checks does not interfere with the federal immigration scheme. Consultation between federal and state officials is an important feature of the immigration system. In fact, Congress has encouraged the sharing of information about possible immigration violations. See §§1357(g)(10)(A), 1373(c). The federal scheme thus leaves room for a policy requiring state officials to contact ICE as a routine matter. Cf. Whiting, 563 U. S., at ___. Pp. 20–21.

(2) It is not clear at this stage and on this record that §2(B), in practice, will require state officers to delay the release of detainees for no reason other than to verify their immigration status. This would raise constitutional concerns. And it would disrupt the federal framework to put state officers in the position of holding aliens in custody for possible unlawful presence without federal direction and supervision. But §2(B) could be read to avoid these concerns. If the law only requires state officers to conduct a status check during the course of an authorized, lawful detention or after a detainee has been released, the provision would likely survive preemption—at least absent some showing that it has other consequences that are adverse to federal law and its objectives. Without the benefit of a definitive interpretation from the state courts, it would be inappropriate to assume §2(B) will be construed in a way that conflicts with federal law. Cf. Fox v. Washington, 236 U. S. 273. This opinion does not foreclose other preemption and constitutional challenges to the law as interpreted and applied after it goes into effect. Pp. 22–24.

641 F. 3d 339, affirmed in part, reversed in part, and remanded.

Kennedy, J., delivered the opinion of the Court, in which Roberts, C. J., and Ginsburg, Breyer, and Sotomayor, JJ., joined. Scalia, J., Thomas, J., and Alito, J., filed opinions concurring in part and dissenting in part. Kagan, J., took no part in the consideration or decision of the case.

Per Curiam.

A Montana state law provides that a “corporation may not make . . . an expenditure in connection with a candidate or a political committee that supports or opposes a candidate or a political party.” Mont. Code Ann. §13– 35–227(1) (2011). The Montana Supreme Court rejected petitioners’ claim that this statute violates the First Amendment. 2011 MT 328, 363 Mont. 220, 271 P. 3d 1. In Citizens United v. Federal Election Commission, this Court struck down a similar federal law, holding that “political speech does not lose First Amendment protection simply because its source is a corporation.” 558 U. S. ___, ___ (2010) (slip op., at 26) (internal quotation marks omitted). The question presented in this case is whether the holding of Citizens United applies to the Montana state law. There can be no serious doubt that it does. See U. S. Const., Art. VI, cl. 2. Montana’s arguments in support of the judgment below either were already rejected in Citizens United, or fail to meaningfully distinguish that case. The petition for certiorari is granted. The judgment of the Supreme Court of Montana is reversed.

It is so ordered.