Executive power

Can someone help explain to whether or not Americans should be concerned if Trump were to overturn the ban through an executive order?

Much as I, of course, hate the ban, it was passed through congress, ratified into law, and found to be not unconstitutional by SCOTUS.

Would Trump overturning this law create any kind of precedent for expanded executive power & open the door to him unilaterally overturning other existing laws or am I just being paranoid?