Also, to reduce the hysteria of this, even if a president has immunity, committing an illegal act and using that immunity would still end up with a legal challenge and that would need to work its way through the courts. Would be a huge headache, and the Supreme Court could very obvious rule differently in a particular case, hinging on what is official and what is on official. I doubt the Supreme Court would look kindly on an assassination of arrival as a “official” act