An essential part of the rule of law is that the rules not be changed in the middle of the game. This principle is embodied in the notion, dating at least from Roman times, that legislation should apply prospectively. Yet, Congress often imposes retroactive liabilities, such as retroactive tax increases, that transgress property rights and fundamental elements of justice. Not only have the courts failed to guard against these liabilities, but, in some cases--most notably in the Superfund context--they imposed retrospective liability where it arguably did not apply. Courts have also failed to enforce constitutional constraints on retroactive legislation.

Daniel E. Troy's study comprehensively traces the history of the presumption of prospectivity. It also surveys the Constitution's ex post facto, bill of attainder, contracts, and takings clauses in documenting the courts' failure to guard against retroactive liability. He concludes that, although retrospective legislation is sometimes unavoidable, political and procedural mechanisms are needed to ensure settled, investment-backed expectations are upset only after careful consideration and when a political consensus exists.

Daniel E. Troy is an associate scholar of legal studies at AEI.