Renault was prominent as an arbitrator, his more famous cases including the Japanese House Tax case of 1905, the Casa Blanca Case of 1909, the Sarvarkar Case of 1911, the Carthage case of 1913, and the Manouba case of 1913. Among his writings are articles and monographs on the specialized topics of international law. Together with his friend and colleague C. Lyon-Caen, he produced several works on commercial law, including a compendium in two volumes, a treatise in eight volumes, and a manual that ran to many editions.
In 1879, Renault published his Introduction to the Study of International Law and in 1917 First Violations of International Law by Germany, concerning the invasion of Belgium and of Luxembourg in breach of Germany's treaty obligations.