Exactly, the US government has three branches, the Executive (President), the Legislative (Congress), and Judicial (courts). The president cannot sign a bill until both the Senate and House of Representatives passes it. The US Supreme court can vacate the law if it is found to be, in their opinion, unconstitutional. The system is based on checks and balances with no one branch having all of the power. Instead of promising to do something during a campaign it may be better just to say what you intend to pursue to the best of your ability. As far a promises are concerned, it seems to me that President Trump is remaining true to his word.