"...clarify whether certain bump stock devices are illegal under current law."

"...to ban all devices that turn legal weapons into machine guns."

Bump stocks are not illegal under current law. The ATF has explicitly approved their sale and use.

Bump stocks also do not "turn legal weapons into machine guns" per the actual legal definition of "fully automatic."

I'm not trying to be a dick, but you're hearing what you want to hear. This is the exact same thing the NRA did after Las Vegas. It looks like "doing something." Any honest reading of current law excludes bump stocks from qualifying as a full auto conversion. Changing that definition would likely require legislative action, by the pro-gun party, in a midterm election year, and actively appearing to do nothing emboldens the opposing party while actively doing something pisses off the base, the people that are most likely to actually vote in a midterm election.

President Trump isn't calling for a ban on bump stocks. He's shifting the responsibility to DoJ and the ATF.