The doctrine and rules of state immunity concern the protection which a state is given from being sued in the courts of other states. The rules relate to legal proceedings in the courts of another state, not in a state's own courts. The rules developed at a time when it was thought to be an infringement of a state's sovereignty to bring proceedings against it or its officials in a foreign country.

There is now a trend in various states towards substantial exceptions to the rule of immunity; in particular, a state can be sued when the dispute arises from a commercial transaction entered into by a state or some other "non-sovereign activity" of a state. The United Nations Convention on Jurisdictional Immunities of States and their Property, which as of 2015 is not yet in force, would re-formulate and harmonise the rules and their exceptions. It does not cover criminal proceedings and it does not allow civil (e.g. financial) actions for human rights abuses against state agents where the abuse has occurred in another country.

In 1938, Lord Atkin observed in the House of Lords, the highest court at the time in the United Kingdom, the following:

The courts of a country will not impede a foreign sovereign, that is, they will not by their process make him against his will a party to legal proceedings whether the proceedings involve process against his person or seek to recover from him specific property or damages.

The rule's wider implication is that a state and any sovereign, unless it chooses to waive its immunity, is immune to the jurisdiction of foreign courts and the enforcement of court orders. So jealously guarded is the law, traditionally the assertion of any such jurisdiction is considered impossible without the foreign power's consent.