"When the President asks you to do something you have only one option, and that is to try to execute what the president asked you to do."
~~ Ambassador McFaul

There is another option. If you know what the president is asking you to do is illegal, you quit, and you tell the whole world why you quit, to do otherwise makes you complicit, and if you have principles then you don't execute the crime.

That would take asking, “Why?” to which the president would answer ...

... any of us could fill in the rest.