Philip C. Jessup’s article “The Reality of International Law” was published in Foreign Affairs, Volume 18, Number 2, in January 1940.
Jessup’s central argument is that international law is real, even though it is weak, often violated, and imperfectly enforced. He rejects the common claim that international law does not exist simply because states break it. For him, violations do not destroy law; they reveal its limits.
The article’s main ideas are:
International law is constantly invoked by states. Governments maintain legal advisers, argue disputes in legal terms, use prize courts, cite treaties, and justify or condemn conduct through legal principles.
International law is weaker than domestic law because it lacks a central legislature, police force, and reliable courts, but this does not make it unreal. Jessup compares it to an early or primitive legal system still developing.
Its effectiveness is most visible in routine affairs: treaties, maritime rules, prisoner-of-war regulations, claims commissions, boundary disputes, communications, transport, labor, health, and other technical fields.
War exposes the failures of international law, especially the failure of the Kellogg-Briand Pact to abolish war. Still, even during war, states continue to invoke neutrality rules, submarine regulations, prize law, and legal claims.
Jessup’s conclusion is pragmatic: international law cannot yet restrain a determined great power, but it remains a functioning part of international society. It is “flouted” and “invoked” repeatedly, yet it continues to shape governmental behavior.
