Federalism in the United States traditionally limits the legislative authority of the federal government in favor of the states. Specifically, the Tenth Amendment of the United States Constitution states that "powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people". Therefore, state governments are free to enact unique laws in any area beyond the purview of federal preemption. Under the doctrine of Erie Railroad Co. v. Tompkins (1938), federal courts cannot dictate law to states on pure issues of state common law (i.e., almost all of contract, tort, and family law). However, a variety of legal issues regularly transcend state lines, which makes a predictable and relatively uniform set of laws across states a desirable objective. "Uniform acts" are collaboratively written model laws intended to facilitate the enactment of identical or similar laws by the separate states. Such laws are distinct from interstate compacts.
