International law is derived from the following sources:
(1) Roman Law, (2) Treaties and international conventions, (3) Conferences and tribunals, (4) Diplomatic correspondence (5) The municipal laws of states.
(1) Roman law:
The Roman law represented a system of law which many European countries borrowed extensively. It is a general code for regulation of relations between state and state in the early period of European history.
(2) Treaties and International Conventions:
Political and commercial alliances constitute another source of International Law. Treaties of Westphalia, Utrecht and Paris signed by a large number of states represent common agreement between nations on various problems.
Conventions like the Geneva Convention of 1864 lay down many rules of international conduct.
(3) Conference and Tribunals:
International conferences and arbitration tribunals while administering existing International law or deciding new questions of international character establish principles which become a part of International Law. The Hague and Washington Conferences have done a great work in this connection.
(4) Diplomatic Correspondence:
Diplomatic correspondence among the diplomatic representatives of big states constitute another source of International Law.
(5) Municipal Law:
Municipal law of every country contains certain statutes having bearing on International Law. For example, laws of citizenship, naturalization, extradition, tariff, army, navy, air force regulations have direct bearing on International Law.