In 1815, the Treaty of Vienna, a multilateral treaty, banished Napoleon Bonaparte after his brutal invasion of Europe. This treaty was a sanction as well as a preventive measure against future aggression, and acted as precedent for the treatment of another sovereign, Wilhelm II of Hohenzollarne, the Kaiser of Germany (1859–1941), who was accused of committing horrific acts against civilians during World War I (Romano, Nollkaemper, & Kleffner, 2004). The Treaty of Versailles, signed in 1919, established a tribunal guided by international policy and international morality of that era to try Wilhelm II for crimes against the laws and customs of war. Kaiser Wilhelm argued that he was a victim of ex post facto or acts made criminal after the fact, and fled. The Netherlands, where he took refuge, refused to extradite Wilhelm (Jorgenson, 1999). Despite the failure to directly punish Kaiser Wilhelm, The Treaty of Versailles was evidence that under certain circumstances the world community would place limits on national sovereignty by international agreement or treaty.
The 1969 Vienna Convention defines a treaty as “an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation.” The 1986 Vienna Convention extends the definition of treaties to include international agreements involving international organizations as parties. Treaties are binding bilateral agreements, as between two States or multilateral agreements, as between several States. These agreements represent one area within the complex system of courts, agreements, customs, principles, and national laws that comprise international law.