<P> The modern study of international law starts in the early 19th century , but its origins go back at least to the 16th century , and Alberico Gentili , Francisco de Vitoria and Hugo Grotius , the `` fathers of international law . '' Several legal systems developed in Europe , including the codified systems of continental European states and English common law , based on decisions by judges and not by written codes . Other areas developed differing legal systems , with the Chinese legal tradition dating back more than four thousand years , although at the end of the 19th century , there was still no written code for civil proceedings . Some doubt the effectiveness of international law , as they see the implementation of international law as a policy option among others to tackle global dilemmas . They say that international law must be evaluated with other , possibly more effective , international law options . </P>
who is often regarded as the father of international law
Alberico Gentili Francisco de Vitoria Hugo Grotius