This is not how it works. First, citizenship is not important in front of a German court barring very few exceptions. Second, there is a law which specifically

This is not how it works. First, citizenship is not important in front of a German court barring very few exceptions. Second, there is a law which specifically protects foreign head of states. Third, German courts ruled before in the past this specific provision is part of international law in the German legal system. You don't need to be a German citizen to be protected by German law (why should you?).