There are certain promises Donald Trump can keep simply by doing nothing. His predecessor embarked on any number of ideological crusades, one of which was to attack gun rights in every manner and in every circumstance available to him, It become incredibly tiresome to see Obama take to the podium and go on an anti-gun rant every time there was a horrific gun crime - as if the crime only happened because Republicans had refused to pass Obama's gun bans.
Gun control is one of the Democratic Party's Holy Grails - up there with abortion and unionization. Every chance they get to push it, they will, regardless of how disingenuous or unconstitutional the effort may be.