“We’ve tried it repeatedly. Often we have failed, but even when we seem to have succeeded, the long-term consequences have been terrible. An order from the Oval Office to assassinate a foreign leader would not break a taboo. It would only be the latest in a series of self-defeating blunders.”
https://www.politico.com/news/magazine/2022/03/13/presidents-ordered-assasinations-us-putin-00016568