Abortion, guns, voting rules, and marijuana law differ dramatically by state because of federalism.
Federalism is the rulebook for which level of government — Washington or your state — gets to decide what.
States can test policies before they go national — and serve as checks when one party controls Washington.
The federal government holds the powers the Constitution lists; the Tenth Amendment reserves the rest to states.
Valid federal law overrides conflicting state law — so the fights are over what federal power validly covers.
Interstate river water is governed by a layered system of state compacts, federal approval, and international treaties — a balance recently tested in the Rio Grande case.
Read the guide →A long-running Rio Grande dispute has reignited debate over how much authority states versus the federal government should hold over shared rivers.
Read the brief →