ATF grabbing ar-15 triggers?

There was no reason to cut them up. Here is the law from the courts..

Federal Ban on Bump Stocks
This was more or less the state of gun control laws in play on the night of October 1, 2017, when a new device, bump stocks, entered the national debate. On that night in Las Vegas, a lone gunman took aim at the gathered crowd below his 37th floor Mandalay suite and opened fire on the attendees of the Route 91 Harvest Music Festival. In ten minutes, with the aid of a bump stock, the shooter unleased over a thousand rounds into the crowd below killing 60 and wounding more than 400 others before dying from a self-inflicted gunshot wound.

Mechanical devices that increase the rate of fire of a semi-automatic weapon, bump stocks use the gun’s recoil to speed the deliver of cartridges to the chamber faster than a person could typically fire the semi-automatic. The Trump Administration’s Justice Department viewed the device as capable of transforming a heretofore legal semi-automatic weapon into an illegal fully automatic rifle for all intents and purpose. The ban was immediately challenged in court as it wound its way through the appellate process before being struck down by the United States 6th District Court of Appeals court that ruled the justice department had exceeded the scope of its authority in issuing the ban. Currently, bump stocks are not illegal in any state since the ruling came down from the appellate court.