opinion: Chief Justice Rehnquist
  delivered the opinion of the Court.
  Petitioner South Dakota permits persons 19 years of age or older to purchase beer containing up to 3.2% alcohol. S. D. Codified Laws §35-6-27 (1986). In 1984 Congress enacted 23 U. S. C. §158 (1982 ed., Supp. III), which directs the Secretary of Transportation to withhold a percentage of federal highway funds otherwise allocable from States “in which the purchase or public possession ... of any alcoholic beverage by a person who is less than twenty-one years of age is lawful.” The State sued in United States District Court seeking a declaratory judgment that § 158 violates the constitutional limitations on congressional exercise of the spending power and violates the Twenty-first Amendment to the United States Constitution. The District Court rejected the State’s claims, and the Court of Appeals for the Eighth Circuit affirmed. 791 F. 2d 628 (1986).
  In this Court, the parties direct most of their efforts to defining the proper scope of the Twenty-first Amendment. Relying on our statement in California Retail Liquor Dealers Assn. v. Midcal Aluminum, Inc., 445 U. S. 97, 110 (1980), that the “Twenty-first Amendment grants the States virtually complete control over whether to permit importation or sale of liquor and how to structure the liquor distribution system,” South Dakota asserts that the setting of minimum drinking ages is clearly within the “core powers” reserved to the States under §2 of the Amendment. Brief for Petitioner 43-44. Section 158, petitioner claims, usurps that core power. The Secretary in response asserts that the Twenty-first Amendment is simply not implicated by § 158; the plain language of § 2 confirms the States’ broad power to impose restrictions on the sale and distribution of alcoholic beverages but does not confer on them any power to permit sales that Congress seeks to prohibit. Brief for Respondent 25-26. That Amendment, under this reasoning, would not prevent Congress from affirmatively enacting a national minimum drinking age more restrictive than that provided by the various state laws; and it would follow a fortiori that the indirect inducement involved here is compatible with the Twenty-first Amendment.
  These arguments present questions of the meaning of the Twenty-first Amendment, the bounds of which have escaped precise definition. Bacchus Imports, Ltd. v. Dias, 468 U. S. 263, 274-276 (1984); Craig v. Boren, 429 U. S. 190, 206 (1976). Despite the extended treatment of the question by the parties, however, we need not decide in this case whether that Amendment would prohibit an attempt by Congress to legislate directly a national minimum drinking age. Here, Congress has acted indirectly under its spending power to encourage uniformity in the States’ drinking ages. As we explain below, we find this legislative effort within constitutional bounds even if Congress may not regulate drinking ages directly.
  The Constitution empowers Congress to “lay and collect Taxes, Duties, Imposts, and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States.” Art. I, § 8, cl. 1. Incident to this power, Congress may attach conditions on the receipt of federal funds, and has repeatedly employed the power “to further broad policy objectives by conditioning receipt of federal moneys upon compliance by the recipient with federal statutory and administrative directives.” Fullilove v. Klutznick, 448 U. S. 448, 474 (1980) (opinion of Burger, C. J.). See Lau v. Nichols, 414 U. S. 563, 569 (1974); Ivanhoe Irrigation Dist. v. McCracken, 357 U. S. 275, 295 (1958); Oklahoma v. Civil Service Comm’n, 330 U. S. 127, 143-144 (1947); Steward Machine Co. v. Davis, 301 U. S. 548 (1937). The breadth of this power was made clear in United States v. Butler, 297 U. S. 1, 66 (1936), where the Court, resolving a longstanding debate over the scope of the Spending Clause, determined that “the power of Congress to authorize expenditure of public moneys for public purposes is not limited by the direct grants of legislative power found in the Constitution.” Thus, objectives not thought to be within Article I’s “enumerated legislative fields,” id., at 65, may nevertheless be attained through the use of the spending power and the conditional grant of federal funds.
  The spending power is of course not unlimited, Pennhurst State School and Hospital v. Halderman, 451 U. S. 1, 17, and n. 13 (1981), but is instead subject to several general restrictions articulated in our cases. The first of these limitations is derived from the language of the Constitution itself: the exercise of the spending power must be in pursuit of “the general welfare.” See Helvering v. Davis, 301 U. S. 619, 640-641 (1937); United States v. Butler, supra, at 65. In considering whether a particular expenditure is intended to serve general public purposes, courts should defer substantially to the judgment of Congress. Helvering v. Davis, supra, at 640, 645. Second, we have required that if Congress desires to condition the States’ receipt of federal funds, it “must do so unambiguously . . . , enabling] the States to exercise their choice knowingly, cognizant of the consequences of their participation.” Pennhurst State School and Hospital v. Halderman, supra, at 17. Third, our cases have suggested (without significant elaboration) that conditions on federal grants might be illegitimate if they are unrelated “to the federal interest in particular national projects or programs.” Massachusetts v. United States, 435 U. S. 444, 461 (1978) (plurality opinion). See also Ivanhoe Irrigation Dist. v. McCracken, supra, at 295, (“[T]he Federal Government may establish and impose reasonable conditions relevant to federal interest in the project and to the over-all objectives thereof”). Finally, we have noted that other constitutional provisions may provide an independent bar to the conditional grant of federal funds. Lawrence County v. Lead-Deadwood School Dist., 469 U. S. 256, 269-270 (1985); Buckley v. Valeo, 424 U. S. 1, 91 (1976) (per curiam); King v. Smith, 392 U. S. 309, 333, n. 34 (1968).
  South Dakota does not seriously claim that §158 is inconsistent with any of the first three restrictions mentioned above. We can readily conclude that the provision is designed to serve the general welfare, especially in light of the fact that “the concept of welfare or the opposite is shaped by Congress . . . .” Helvering v. Davis, supra, at 645. Congress found that the differing drinking ages in the States created particular incentives for young persons to combine their desire to drink with their ability to drive, and that this interstate problem required a national solution. The means it chose to address this dangerous situation were reasonably calculated to advance the general welfare. The conditions upon which States receive the funds, moreover, could not be more clearly stated by Congress. See 23 U. S. C. § 158 (1982 ed., Supp. III). And the State itself, rather than challenging the germaneness of the condition to federal purposes, admits that it “has never contended that the congressional action was . . . unrelated to a national concern in the absence of the Twenty-first Amendment.” Brief for Petitioner 52. Indeed, the condition imposed by Congress is directly related to one of the main purposes for which highway funds are expended — safe interstate travel. See 23 U. S. C. § 101(b). This goal of the interstate highway system had been frustrated by varying drinking ages among the States. A Presidential commission appointed to study alcohol-related accidents and fatalities on the Nation’s highways concluded that the lack of uniformity in the States’ drinking ages created “an incentive to drink and drive” because “young persons commute] to border States where the drinking age is lower.” Presidential Commission on Drunk Driving, Final Report 11 (1983). By enacting § 158, Congress conditioned the receipt of federal funds in a way reasonably calculated to address this particular impediment to a purpose for which the funds are expended.
  The remaining question about the validity of § 158 — and the basic point of disagreement between the parties — is whether the Twenty-first Amendment constitutes an “independent constitutional bar” to the conditional grant of federal funds. Lawrence County v. Lead-Deadwood School List., supra, at 269-270. Petitioner, relying on its view that the Twenty-first Amendment prohibits direct regulation of drinking ages by Congress, asserts that “Congress may not use the spending power to regulate that which it is prohibited from regulating directly under the Twenty-first Amendment.” Brief for Petitioner 52-53. But our cases show that this “independent constitutional bar” limitation on the spending power is not of the kind petitioner suggests. United States v. Butler, supra, at 66, for example, established that the constitutional limitations on Congress when exercising its spending power are less exacting than those on its authority to regulate directly.
  We have also held that a perceived Tenth Amendment limitation on congressional regulation of state affairs did not concomitantly limit the range of conditions legitimately placed on federal grants. In Oklahoma v. Civil Service Comm’n, 330 U. S. 127 (1947), the Court considered the validity of the Hatch Act insofar as it was applied to political^ activities of state officials whose employment was financed in whole or in part with federal funds. The State contended that an order under this provision to withhold certain federal funds unless a state official was removed invaded its sovereignty in violation of the Tenth Amendment. Though finding that “the United States is not concerned with, and has no power to regulate, local political activities as such of state officials,” the Court nevertheless held that the Federal Government “does have power to fix the terms upon which its money allotments to states shall be disbursed.” Id., at 143. The Court found no violation of the State’s sovereignty because the State could, and did, adopt “the ‘simple expedient’ of not yielding to what she urges is federal coercion. The offer of benefits to a state by the United States dependent upon cooperation by the state with federal plans, assumedly for the general welfare, is not unusual.” Id., at 143-144 (citation omitted). See also Steward Machine Co. v. Davis, 301 U. S., at 595 (“There is only a condition which the state is free at pleasure to disregard or to fulfill”); Massachusetts v. Mellon, 262 U. S. 447, 482 (1923).
  These cases establish that the “independent constitutional bar” limitation on the spending power is not, as petitioner suggests, a prohibition on the indirect achievement of objectives which Congress is not empowered to achieve directly. Instead, we think that the language in our earlier opinions stands for the unexceptionable proposition that the power may not be used to induce the States to engage in activities that would themselves be unconstitutional. Thus, for example, a grant of federal funds conditioned on invidiously discriminatory state action or the infliction of cruel and unusual punishment would be an illegitimate exercise of the Congress’ broad spending power. But no such claim can be or is made here. Were South Dakota to succumb to the blandishments offered by Congress and raise its drinking age to 21, the State’s action in so doing would not violate the constitutional rights of anyone.
  Our decisions have recognized that in some circumstances the financial inducement offered by Congress might be so coercive as to pass the point at which “pressure turns into compulsion.” Steward Machine Co. v. Davis, supra, at 590. Here, however, Congress has directed only that a State desiring to establish a minimum drinking age lower than 21 lose a relatively small percentage of certain federal highway funds. Petitioner contends that the coercive nature of this program is evident from the degree of success it has achieved. We cannot conclude, however, that a conditional grant of federal money of this sort is unconstitutional simply by reason of its success in achieving the congressional objective.
  When we consider, for a moment, that all South Dakota would lose if she adheres to her chosen course as to a suitable minimum drinking age is 5% of the funds otherwise obtainable under specified highway grant programs, the argument as to coercion is shown to be more rhetoric than fact. As we said a half century ago in Steward Machine Co. v. Davis:
  “[Ejvery rebate from a tax when conditioned upon conduct is in some measure a temptation. But to hold that motive or temptation is equivalent to coercion is to plunge the law in endless difficulties. The outcome of such a doctrine is the acceptance of a philosophical determinism by which choice becomes impossible. Till now the law has been guided by a robust common sense which assumes the freedom of the will as a working hypothesis in the solution of its problems.” 301 U. S., at 589-590.
  Here Congress has offered relatively mild encouragement to the States to enact higher minimum drinking ages than they would otherwise choose. But the enactment of such laws remains the prerogative of the States not merely in theory but in fact. Even if Congress might lack the power to impose a national minimum drinking age directly, we conclude that encouragement to state action found in § 158 is a valid use of the spending power. Accordingly, the judgment of the Court of Appeals is
  Affirmed.
  Section 2 of the Twenty-first Amendment provides: “The transportation or importation into any State, Territory, or possession of the United States for delivery or use therein of intoxicating liquors, in violation of the laws thereof, is hereby prohibited.”
  The level of deference to the congressional decision is such that the Court has more recently questioned whether “general welfare” is a judicially enforceable restriction at all. See Buckley v. Valeo, 424 U. S. 1, 90-91 (1976) (per curiam).
  Our cases have not required that we define the outer bounds of the “germaneness” or “relatedness” limitation on the imposition of conditions under the spending power. Amici urge that we take this occasion to establish that a condition on federal funds is legitimate only if it relates directly to the purpose of the expenditure to which it is attached. See Brief for National Conference of State Legislatures et al. as Amici Curiae 10. Because petitioner has not sought such a restriction, see Tr. of Oral Arg. 19-21, and because we find any such limitation on conditional federal grants satisfied in this ease in any event, we do not address whether conditions less directly related to the particular purpose of the expenditure might be outside the bounds of the spending power.
choices: stay, petition, or motion granted affirmed reversed reversed and remanded vacated and remanded affirmed and reversed (or vacated) in part affirmed and reversed (or vacated) in part and remanded vacated petition denied or appeal dismissed modify remand unusual disposition