Undoubtedly, the expansion of the UCMJ to contractors and other persons accompanying or serving with the armed forces in the field will be challenged on constitutional grounds. But is this legislation unconstitutional? This article discusses the Supreme Court cases that have addressed the constitutionality of the application of the military law and court-martial jurisdiction to civilians, the Supreme Court decisions that may provide insight into the Court’s views of military jurisdiction, and how today’s Court might address the constitutionality of this expansion of UCMJ jurisdiction in light of recommendations made by the DoD on implementation and withholding of UCMJ convening authority. Part II of this article discusses the legislative expansion of UCMJ jurisdiction, and Part III discusses the Joint Service Committee recommendations on implementation of this expansion. Part IV discusses Supreme Court cases relevant to application of court-martial jurisdiction to civilians, and Part V briefly discusses current similarities and differences between civil court and court-martial procedure. Finally, Part VI attempts to predict whether the Supreme Court would find various applications of the UCMJ to contractors constitutional.