Federalism is a system under which the powers and sovereignty are constitutionally divided between the national (federal) government and the constituent units (states). Under federalism, citizens are subject to federal, state, and local laws. James Madison and Alexander Hamilton advocated for a federal government in an essay series called the Federalist. As framers of the 1789 US constitution, they created the model of modern federalism that was later followed by other federal countries. The model's key element is the supremacy clause, which states law is invalid (unenforceable) if it conflicts with the federal law. The U.S. has followed various models of federalism in its history. During the 1960s, it pursued creative federalism. Under cooperative federalism, states and the federal government have common goals, and the federal government supports states with grants.