A more thorough explanation:

Definition: Locus regit actum is a Latin term that means "the place rules the act." In international law, it refers to the principle that a transaction that follows the legal formalities of the country where it is created will be considered valid in the country where it is to be effective, even if that country requires additional formalities.

For example, if a contract is created in the United States and follows all the legal formalities required by U.S. law, it will be considered valid in another country, such as Canada, even if Canadian law requires additional formalities.

Another example is a will that is created in France and follows all the legal formalities required by French law. If the person who created the will dies while in the United Kingdom, the will would still be considered valid in the UK, even if UK law requires additional formalities.

These examples illustrate how the principle of locus regit actum works in international law. As long as a transaction follows the legal formalities of the country where it is created, it will be recognized as valid in other countries, even if those countries have different requirements.