I'm just taking a stab in the dark here, but I'd say that if the current administration was able to engineer some sort of ban, it would have to increase the staffing of the ATF to something approaching the size of the Army to proactively enforce it.
Remember, the ATF isn't a particularly large bureau and they deal with more than just guns. As an anecdotal note, I inherited an old Colt New Army/Navy revolver a few years back that my great grandfather got in some sort of trade. Somebody had filed off the serial number before he got it. I called the local ATF office and asked if it was something that I should be concerned about. The agent actually laughed. He said that something like that was so low on their priority list that they'd have to have solved every case that they'd ever had and maybe even discovered world peace before they'd even give a thought to looking into it. At least around here, they're busy as all get-out now without taking on any fresh duties.
Well we don't rent pigs and I figure it's better to say it right out front because a man that does like to rent pigs is... he's hard to stop - Gus McCrae