 Among the most influential elements in the works from the School of Salamanca are those connected to what was called the ius gentium until the late eighteenth century but is nowadays referred to as international law. Firstly, they separated the ius gentium from natural law, with which it had more or less been identified with since the formulation of Roman Law; secondly, they developed a martial law on the basis of quaestio 40 in the Secunda secundae of Thomas Aquinas’s Summa theologiae; and thirdly, they treated the alleged right to enslave non-European human beings.