What distinguishes Hugo Grotius was an overriding concern to reconcile the ideal of popular liberty, on the one hand, with the necessity of civil government, on the other. Grotius offers a novel theory of liberty that is not opposed to the power of government, but instead, is parasitic upon it. One surprising result from this analysis is the view that, in special circumstances, a people may remain free even while under the government of a prince. The chapter investigates the varieties of arguments from Roman law deployed by Grotius to conceptualize the status and the rights of the populus liber. It assesses how such a free people can be governed without also curtailing their liberty. Grotius's argument approximating princely government to ususfructus, rather than to dominus, was framed within the analysis on property which plays a central role in the argument of De jure Belli ac Pacis.