Grotius’s theory of punishment provides a unique lens through which to view his evolving thought on sovereignty between De Indis and De iure belli ac pacis and the implications of that evolution for Grotius’s theory of the ius in bello. Throughout both works, Grotius attempted to leave open the possibility of private punishment and private warfare, a position not easily squared with prevailing views of sovereign authority. Initially, Grotius was content with a theory marrying the private right of punishment with more traditional Scholastic views of sovereignty through a transfer of the private right from individuals into the hands of the sovereign. This theory also adopted traditional views of subject responsibility for sovereign acts—and, by extension, the exposure of subjects to punishment for the acts of their sovereign. By the time of his mature work, however, Grotius turned away from natural law justifications for collective responsibility and collective punishment, denying that subjects had to answer for the acts of their sovereign as a necessary incident of the compact creating civil society. This led Grotius to refer virtually all forms of collective responsibility, such as reprisal or punishment exacted through war, to the law of nations. This sharp reduction of the natural consequences of the creation of sovereign power also enabled Grotius’s argument that the private right of war, and in particular the private right of punishment, remained available after the creation of civil society.