SCALIA, J., concurring in judgment

foster and protect the commerce, but embraces those which prohibit it." Darby, 312 U. S., at 113. See also Hipolite Egg Co. v. United States, 220 U. S. 45, 58 (1911); Lottery Case, 188 U. S. 321, 354 (1903). To effectuate its objective, Congress has prohibited almost all intrastate activities related to Schedule I substances-both economic activities (manufacture, distribution, possession with the intent to distribute) and noneconomic activities (simple possession). See 21 U. S. C. §§ 841(a), 844(a). That simple possession is a noneconomic activity is immaterial to whether it can be prohibited as a necessary part of a larger regulation. Rather, Congress's authority to enact all of these prohibitions of intrastate controlled-substance activities depends only upon whether they are appropriate means of achieving the legitimate end of eradicating Schedule I substances from interstate commerce.

By this measure, I think the regulation must be sustained. Not only is it impossible to distinguish "controlled substances manufactured and distributed intrastate" from "controlled substances manufactured and distributed interstate," but it hardly makes sense to speak in such terms. Drugs like marijuana are fungible commodities. As the Court explains, marijuana that is grown at home and possessed for personal use is never more than an instant from the interstate market-and this is so whether or not the possession is for medicinal use or lawful use under the laws of a particular State.3

3 The principal dissent claims that, if this is sufficient to sustain the regulation at issue in this case, then it should also have been sufficient to sustain the regulation at issue in United States v. Lopez, 514 U. S. 549 (1995). See post, at 52 (arguing that "we could have surmised in Lopez that guns in school zones are 'never more than an instant from the interstate market' in guns already subject to extensive federal regulation, recast Lopez as a Necessary and Proper Clause case, and thereby upheld the Gun-Free School Zones Act" (citation omitted)). This claim founders upon the shoals of Lopez itself, which made clear that the statute there at issue was "not an essential part of a larger regulation of economic activity." Lopez, supra, at 561 (emphasis added). On the dissent's view of things,

SCALIA, J., concurring in judgment

See ante, at 25-33. Congress need not accept on faith that state law will be effective in maintaining a strict division between a lawful market for "medical" marijuana and the more general marijuana market. See ante, at 30, and n. 38. "To impose on [Congress] the necessity of resorting to means which it cannot control, which another government may furnish or withhold, would render its course precarious, the result of its measures uncertain, and create a dependence on other governments, which might disappoint its most important designs, and is incompatible with the language of the constitution." McCulloch, 4 Wheat., at 424.

Finally, neither respondents nor the dissenters suggest any violation of state sovereignty of the sort that would render this regulation "inappropriate," id., at 421-except to argue that the CSA regulates an area typically left to state regulation. See post, at 48, 51 (opinion of O'CONNOR, J.); post, at 66 (opinion of THOMAS, J.); Brief for Respondents 39-42. That is not enough to render federal regulation an inappropriate means. The Court has repeatedly recognized that, if authorized by the commerce power, Congress may regulate private endeavors "even when [that regulation] may pre-empt express state-law determinations contrary to the result which has commended itself to the collective wisdom of Congress." National League of Cities v. Usery, 426 U. S. 833, 840 (1976); see Cleveland v. United States, 329 U. S. 14, 19 (1946); McCulloch, supra, at 424. At bottom, respond

that statement is inexplicable. Of course it is in addition difficult to imagine what intelligible scheme of regulation of the interstate market in guns could have as an appropriate means of effectuation the prohibition of guns within 1,000 feet of schools (and nowhere else). The dissent points to a federal law, 18 U. S. C. § 922(b)(1), barring licensed dealers from selling guns to minors, see post, at 52-53, but the relationship between the regulatory scheme of which § 922(b)(1) is a part (requiring all dealers in firearms that have traveled in interstate commerce to be licensed, see § 922(a)) and the statute at issue in Lopez approaches the nonexistent-which is doubtless why the Government did not attempt to justify the statute on the basis of that relationship.

O'CONNOR, J., dissenting

ents' state-sovereignty argument reduces to the contention that federal regulation of the activities permitted by California's Compassionate Use Act is not sufficiently necessary to be "necessary and proper" to Congress's regulation of the interstate market. For the reasons given above and in the Court's opinion, I cannot agree.

I thus agree with the Court that, however the class of regulated activities is subdivided, Congress could reasonably conclude that its objective of prohibiting marijuana from the interstate market "could be undercut" if those activities were excepted from its general scheme of regulation. See Lopez, 514 U. S., at 561. That is sufficient to authorize the application of the CSA to respondents.

JUSTICE O'CONNOR, with whom THE CHIEF JUSTICE and JUSTICE THOMAS join as to all but Part III, dissenting.

We enforce the "outer limits" of Congress' Commerce Clause authority not for their own sake, but to protect historic spheres of state sovereignty from excessive federal encroachment and thereby to maintain the distribution of power fundamental to our federalist system of government. United States v. Lopez, 514 U. S. 549, 557 (1995); NLRB v. Jones & Laughlin Steel Corp., 301 U. S. 1, 37 (1937). One of federalism's chief virtues, of course, is that it promotes innovation by allowing for the possibility that “a single courageous State may, if its citizens choose, serve as a laboratory; and try novel social and economic experiments without risk to the rest of the country." New State Ice Co. v. Liebmann, 285 U. S. 262, 311 (1932) (Brandeis, J., dissenting).

This case exemplifies the role of States as laboratories. The States' core police powers have always included authority to define criminal law and to protect the health, safety, and welfare of their citizens. Brecht v. Abrahamson, 507 U. S. 619, 635 (1993); Whalen v. Roe, 429 U. S. 589, 603,

O'CONNOR, J., dissenting

n. 30 (1977). Exercising those powers, California (by ballot initiative and then by legislative codification) has come to its own conclusion about the difficult and sensitive question of whether marijuana should be available to relieve severe pain and suffering. Today the Court sanctions an application of the federal Controlled Substances Act that extinguishes that experiment, without any proof that the personal cultivation, possession, and use of marijuana for medicinal purposes, if economic activity in the first place, has a substantial effect on interstate commerce and is therefore an appropriate subject of federal regulation. In so doing, the Court announces a rule that gives Congress a perverse incentive to legislate broadly pursuant to the Commerce Clause-nestling questionable assertions of its authority into comprehensive regulatory schemes-rather than with precision. That rule and the result it produces in this case are irreconcilable with our decisions in Lopez, supra, and United States v. Morrison, 529 U. S. 598 (2000). Accordingly I dissent.

I

In Lopez, we considered the constitutionality of the GunFree School Zones Act of 1990, which made it a federal offense "for any individual knowingly to possess a firearm . . . at a place that the individual knows, or has reasonable cause to believe, is a school zone," 18 U. S. C. § 922(q)(2)(A). We explained that "Congress' commerce authority includes the power to regulate those activities having a substantial relation to interstate commerce, i. e., those activities that substantially affect interstate commerce." 514 U. S., at 558-559 (citation omitted). This power derives from the conjunction of the Commerce Clause and the Necessary and Proper Clause. Garcia v. San Antonio Metropolitan Transit Authority, 469 U. S. 528, 585-586 (1985) (O'CONNOR, J., dissenting) (explaining that United States v. Darby, 312 U. S. 100 (1941), United States v. Wrightwood Dairy Co., 315 U. S. 110 (1942), and Wickard v. Filburn, 317 U. S. 111 (1942),

O'CONNOR, J., dissenting

based their expansion of the commerce power on the Necessary and Proper Clause, and that "the reasoning of these cases underlies every recent decision concerning the reach of Congress to activities affecting interstate commerce"); ante, at 34 (SCALIA, J., concurring in judgment). We held in Lopez that the Gun-Free School Zones Act could not be sustained as an exercise of that power.

Our decision about whether gun possession in school zones substantially affected interstate commerce turned on four considerations. Lopez, supra, at 559-567; see also Morrison, supra, at 609-613. First, we observed that our “substantial effects" cases generally have upheld federal regulation of economic activity that affected interstate commerce, but that § 922(q) was a criminal statute having "nothing to do with 'commerce' or any sort of economic enterprise." Lopez, 514 U. S., at 561. In this regard, we also noted that “[s]ection 922(q) is not an essential part of a larger regulation of economic activity, in which the regulatory scheme could be undercut unless the intrastate activity were regulated. It cannot, therefore, be sustained under our cases upholding regulations of activities that arise out of or are connected with a commercial transaction, which viewed in the aggregate, substantially affects interstate commerce." Ibid. Second, we noted that the statute contained no express jurisdictional requirement establishing its connection to interstate commerce. Ibid.

Third, we found telling the absence of legislative findings about the regulated conduct's impact on interstate commerce. We explained that while express legislative findings are neither required nor, when provided, dispositive, findings "enable us to evaluate the legislative judgment that the activity in question substantially affect[s] interstate commerce, even though no such substantial effect [is] visible to the naked eye." Id., at 563. Finally, we rejected as too attenuated the Government's argument that firearm possession in school zones could result in violent crime which in turn could