In South Dakota v. Dole (1987), the Supreme Court upheld a federal law that withheld 5% of highway funds from states that allowed drinking below age 21. The Court established a four-part test: the spending must serve the general welfare; conditions must be unambiguous; conditions must relate to the program's federal interest; and the financial pressure must not be coercive. The ruling gave the federal government broad leverage over states through spending conditions, a power the Trump administration invokes when withholding Medicaid funds to pressure Democratic-led states.