Federal laws require a federal law enforcement agency That said, there' isn't any reason the enforcement of all federal laws cannot be handled by the FBI and US Marshall service.
You should be careful what you wish for. There is no question that Alcohol and Tobacco need regulated as well as Firearms. But it needs to be done in a way that serves the public, not criminalize it or persecute it. I think (hope) once they get their hands slapped over the current Pistol/SBR fiasco maybe all sides will come to OUR senses and do away with bad gun law and initiate social reform that provides a more equitable America for everyone and looks after people that have been left behind in the most prosperous nation on earth. There's a lot of talk about compromise, maybe the Pro 2A crowd could trade more thorough background checks for elimination of bad gun law like they have in California that just pisses gun people off and saves zero lives. Maybe we could provide better, proactive mental health care in exchange for minimum requirements of knowledge and competency for gun owners. If we could start addressing the societal inequities that are the root of our social problems and violence and start investing in the well being of the least of Americans "I" believe we would see a drop in violence AND an equal drop in the call for gun-grabbing.