What laws are Trump subject to?

Trump seems to think that as president he is above the law. Suppose that a law was passed saying the president must place private savings in a blind trust. I don’t think this is likely, but just suppose for the moment that it happens. What if Trump refuses to comply? What happens?

During the election, Trump said that he could shoot someone in a New York crowd and nothing would happen. What if he did that as president? Who would arrest him or put him on trial? If he was impeached, could he be arrested and tried afterward?