In this article, the author compares U.S. Constitutional law addressing "regulatory takings," including substantive due process, with analogous international investment law reviewing regulatory expropriations. Many of the concepts underlying the U.S. approach towards substantive due process appear in discussions of the meaning of international investment law protections, particularly the "Fair and Equitable Treatment" (F&ET) obligation. The article first reviews direct efforts by the U.S. Government to harmonize U.S. Constitutional practice and international law with respect to regulatory expropriations. It then considers how the U.S. substantive due process and procedural due process approaches towards regulation of property interests compare with the developing body of F&ET decisions and commentary concerning regulatory conduct of a host State.