In 1996 Congress passed two laws, the Antiterrorism and Effective Death Penalty Act of 1996 and the Illegal Immigration Reform and Immigrant Responsibility Act of 1996, which substantially increased the likelihood that permanent residents will be deported from the United States for criminal convictions. The deportation provisions of these 1996 laws are now being applied retroactively to immigrants who could not or would not have been deported under the law in place at the time the immigrants were convicted for their offenses. Noting the potential injustice of this change in the rules by which immigrants were expected to conduct their lives, Professor Morawetz explores the constitutionality of the retroactive application of these new deportation schemes. Rather than relying upon a traditional ex post facto analysis, however, Professor Morawetz examines how the retroactive application of these laws may offend the Due Process Clause as it has been interpreted and applied in a body of Supreme Court case law addressing economic legislation. The plenary power doctrine alone, Professor Morawetz argues, does not bar the courts from testing the retroactive application of these deportation provisions according to the substantive due process standard enunciated by the Court. In fact, courts may be forced to address the constitutionality of the deportation provisions due to jurisdictional restrictions contained in the 1996 laws. After analyzing the history and text of the 1996 legislation, Professor Morawetz concludes that it would be unconstitutional to apply retroactively many, if not all of these deportation provisions to immigrants whose conduct and convictions occurred prior to the implementation of Congress’s new scheme.