In the case of of South Dakota v. Dole (483 U.S. 203 (1987)), the Federal government was attempting to withhold federal highway funds from States that did not pass a minimum drinking age of 21. States sued, claiming that Congress was acting unconstitutionally because under the 21st Amendment, the power to regulate alcohol fell mainly to the States. The US Supreme Court upheld the law, and found that there were several conditions to deciding if a law met the conditions to be legal under the Spending Clause.
- The tax must be in pursuit of the general welfare.
- It must be unambiguous. There can’t be a failed understanding of what is expected of the States.
- It must be related to the Federal interest in particular national projects of programs.
- It must not violate any other Constitutional provisions.