So according to NPR the Lt. Governor of Massachusetts signed an appropriations bill that included the ban of the devices. Owners of the devices in Massachusetts have 90 days to destroy/discard/etc the devices or they become criminals.
Massachusetts Becomes 1st State To Ban Bump Stocks After Las Vegas Massacre : The Two-Way : NPR
On Facebook the comments under NRP's post linking to the story is interesting. Most there don't see the issue with making people criminals after the fact for buying something legally before the bill was created. One guy even equated it to what happened to Asbestos, lead paint or leaded gasoline. One person pointed out that owing a lead painted asbestos shingled house didn't make you a criminal, and instead those were phased out instead of just being making the owners criminals.
Massachusetts Becomes 1st State To Ban Bump Stocks After Las Vegas Massacre : The Two-Way : NPR
On Facebook the comments under NRP's post linking to the story is interesting. Most there don't see the issue with making people criminals after the fact for buying something legally before the bill was created. One guy even equated it to what happened to Asbestos, lead paint or leaded gasoline. One person pointed out that owing a lead painted asbestos shingled house didn't make you a criminal, and instead those were phased out instead of just being making the owners criminals.