According to the preamble to contract law, treaties are a source of international law. If an act or absence is condemned by international law, the law will not accept its international legality, even if it is authorized by domestic law.  This means that in the event of a conflict with domestic law, international law will always prevail.  Under international law, a treaty is a legally binding agreement between states (countries). A treaty can be called a convention, protocol, pact, agreement, etc. It is the content of the agreement, not its name, that makes it a treaty. Thus, the Geneva Protocol and the Biological Weapons Convention are the two treaties, although neither treaty in its name. Under U.S. law, a treaty is a legally binding agreement between countries that requires ratification and “consultation and approval” of the Senate. All other agreements (internationally treated) are called executive agreements, but are nevertheless legally binding on the United States under international law. A treaty is a formal and binding written agreement that is concluded by actors in international law, usually sovereign states and international organizations, but may involve individuals and other actors.
 A treaty can also be described as an international agreement, protocol, treaty, convention, pact or exchange of letters. Regardless of terminology, only instruments that are binding on the parties are considered treaties of international law.  A treaty is binding under international law. An essential part of treaty drafting is that the signing of a treaty implies recognition, that the other party is a sovereign state and that the agreement, considered to be under international law, is applicable. Therefore, nations can be very cautious when it comes to qualifying a treaty agreement. In the United States, for example, interstate agreements are pacts and agreements between states and the federal government or between government authorities are statements of intent. Treaties were an important part of European colonization and, in many parts of the world, Europeans tried to legitimize their sovereignty by signing treaties with indigenous peoples. In most cases, these contracts were in extremely unfavourable terms for Aboriginal people, who often did not understand the effects of what they signed. [Citation required] In the case of indigenous Australians, no treaty has ever been concluded with indigenous peoples who hate Europeans to own land, with the doctrine of terra nullius (with the exception of Southern Australia) largely being taken up. This concept was then overturned by Mabo v Queensland, which established the concept of indigenous title in Australia long after colonization was a fait accompli.