Whether Congress may condition a portion of federal highway funds on a State's adoption of a minimum drinking age of 21 under the Spending Clause.
Holding
Yes. Section 158 is a valid exercise of Congress's spending power.
Reasoning
Congress's power to spend for the general welfare is not confined to matters within its enumerated powers to regulate directly. It may therefore use conditional grants to encourage States to pursue federal policy objectives, so long as the conditions satisfy constitutional limits.
The Court identified four general limits on conditional federal spending: the spending must serve the general welfare; Congress must state the condition unambiguously; the condition must be related to the federal interest in the funded program; and the condition may not require States to undertake unconstitutional conduct.
Section 158 served the general welfare. Congress found that differing state drinking ages encouraged young people to cross state borders to drink and then drive, creating a national highway-safety problem. Courts give substantial deference to Congress's judgment about what promotes the general welfare.
The condition was unmistakably clear: a State that allowed persons under 21 to purchase or publicly possess alcohol would lose 5% of otherwise available funds under specified highway-grant programs. States could therefore decide knowingly whether to accept the condition and its consequences.
The drinking-age condition was sufficiently related to the federal highway program. Highway funds serve, among other purposes, safe interstate travel, and Congress reasonably concluded that a uniform drinking age would reduce alcohol-related dangers associated with interstate driving and border crossings.
The financial consequence was not unconstitutionally coercive. A 5% reduction in a defined category of highway funds was relatively mild encouragement, not compulsion. A conditional funding offer does not become unconstitutional merely because it effectively persuades States to alter their policies.