The first rule is that the courts of this country will recognise, and will not question, the effect of a foreign state’s legislation or other laws in relation to any acts which take place or take effect within the territory of that state.
The second rule is that the courts of this country will recognise, and will not question, the effect of an act of a foreign state’s executive in relation to any acts which take place or take effect within the territory of that state.
The third rule has more than one component, but each component involves issues which are inappropriate for the courts of the United Kingdom to resolve because they involve a challenge to the lawfulness of the act of a foreign state which is of such a nature that a municipal judge cannot or ought not rule on it [eg involving the making of war and peace, making treaties with foreign sovereigns, annexations of territory and the legality of acts of a foreign government in the conduct of foreign affairs].
A possible fourth rule was described by Rix LJ in a judgment on behalf of the Court of Appeal in Yukos Capital SARL v OJSC Rosneft Oil Co (No 2) ... as being that “the courts will not investigate acts of a foreign state where such an investigation would embarrass the government of our own country: but that this doctrine only arises as a result of a communication from our own Foreign Office”.