How did Hugo Grotius help develop the modern legal principle of agency?

Hugo Grotius played a pivotal role in the development of the modern legal principle of agency by helping to overcome restrictive Roman legal traditions during the 17th-century ascendancy of natural law.1

In his seminal work, On the Law of War and Peace (1625), Grotius argued that a procurator (agent) could acquire rights directly for a principal based on a mandate. This challenged the prevailing Roman rule, which generally restricted direct representation to slaves and dependent sons acting for a head of household, while excluding free persons. Grotius maintained that allowing free persons to act as agents did not contradict natural law.1

Furthermore, in Defensio Fidei Catholicae, Grotius provided a theological and philosophical foundation for the concept, asserting that agency is not demanded by the essential nature of things but must be adapted to them—a principle categorized as nonessential natural law. By decoupling agency from rigid Roman constraints, Grotius helped establish the framework for modern representation in civil law systems.1