In other cases, such as New Zealand with the Maori and Canada with its First Nations and First Nations, treaties have allowed Aboriginal people to maintain a modicum of autonomy. Such agreements between colonizers and indigenous peoples are an important part of the political discourse of the late 20th and early 21st centuries, the treaties that are being discussed have an international reputation, as indicated by a UN treaty study.   There are three ways to amend an existing contract. First, a formal change requires that States Parties be forced to go through the ratification process again. The renegotiation of the treaty provisions can be long and time-consuming and often some parties to the original treaty will not become parties to the amended treaty. In determining the legal obligations of states, a party to the original treaty and a party to the amended treaty, states are bound only by the conditions on which they have agreed. Contracts may also be amended informally by the treaty office if the amendments are procedural in nature, and technical changes in customary international law may also alter a contract in which the state`s conduct presents a reinterpreting interpretation of legal obligations arising from the treaty. Minor corrections to a contract may be accepted by a minutes; However, a minutes are generally reserved for amendments to correct obvious errors in the adopted text, i.e. where the adopted text does not adequately reflect the parties` intention to adopt it. Before 1871, the U.S. government regularly entered into contracts with Indians, but the Indians Appropriation Act of March 3, 1871 (Chapter 120, 16 Stat. 563) had a horseman (25 US. C No.
71), which effectively ended the drafting of presidential treaties by declaring that no Indian nation or Indian tribe can be recognized as a nation, tribe or independent power with which the United States can enter into contractual contracts. After 1871, the federal government continued to maintain similar contractual relations with Indian tribes through agreements, statutes and executive ordinances.  Australian contracts are generally covered by the following categories: delivery, postal agreements and fund orders, trade and international conventions. Articles 46-53 of the Vienna Convention on Treaty Law define the only ways to declare treaties invalid – which is considered unenforceable and void in international law. A treaty is invalidated either because of the circumstances in which a State party has acceded to the treaty, or because of the very content of the treaty. Cancellation is separate from termination, suspension or termination (addressed above), all of which involve a change in the consent of the parties to a previously valid contract, not the nullity of that consent in the first place. In the United States, the term „treaty“ has a different, more limited legal meaning than in international law. U.S. legislation distinguishes what it calls „treaties“ from „executive agreements“ that are either „executive agreements of Congress“ or „single executive agreements.“ Classes are all treatises of international law in the same way; they differ only in U.S. domestic law. In India, the themes are divided into three lists: the Union, the State and the Simultaneous.