The Tenth Amendment reserves to the states and the people all powers not conferred on Congress by the Constitution.  The Constitution does not grant Congress the power to direct state legislatures to enact or refrain from enacting specific legislation.  Congress may not commandeer the states’ legislative process by directly compelling them to enact and enforce a federal regulatory program or prohibit other conduct.  The Professional and Amateur Sports Protection Act (28 USC 3702) violates this principle by prohibiting states from authorizing sports betting.  The act does not directly regulate private actors, but only tells state legislatures what they may not enact.

United States Supreme Court (Alito, J.; Thomas, J., concurring; Breyer, J., concurring in part & dissenting in part; Ginsburg & Sotomayor, JJ., dissenting); May 14, 2018; 2018 U.S. LEXIS 2805