Abstract
Many of the U.S. Supreme Court's recent decisions have embraced federalism-except in one notable area. Modern Supreme Court Fifth Amendment takings cases have paradoxically diminished the role and importance of state law. Doing so creates uncertainty and unpredictability in determining where private property rights begin and where government's authority ends. The parameters of a property interest, the applicable venue, and the definition of "background principles" that limit takings claims are all subject to judicially created factors that are outside the realm of state law. Property interests are historically defined by state laws, and takings law is arguably the archetypal realm of state law. But contemporary takings cases contrast with other recent cases where the Court has enthusiastically embraced federalism. The Court has furthered federalism in access to the right of abortion and in the reach of climate change regulation, but not in the core area of property law, which is a traditional bastion of state authority under the Tenth Amendment.