You could have stopped the sentence here; most US presidents are responsible for acts that appear to be criminal but for the fact that it is political convention not to charge them. The most egregious case I recall was Anwar Al-Awlaki [0] - where he seems to have been killed on the president's orders without actually having done anything specific to justify it. Searching for "crime" on his Wikipedia page turns up nothing much. If a president isn't publicly investigated by the judicial system for having a US citizen killed it is hard to see when charges would be appropriate.