The same law that permits them to abolish the IRS, Obamacare, Education, EPA, etc.....NONE...No president can do that without an executive order. It’s Congress. ALL the candidates play the same game. The difference is, I believe Trump will actually get the leadership of Congress together and cajole them to do it.
I think that a lot of the stuff in obamacare was added in later with Executive Orders. I’m guessing it is the same on all of the other things too. One could declare all of those EO’s void and probably put a big dent in things.