The federal definition of a machine gun is a firearm that is capable of firing more than one round with a single pull of the trigger. Forced reset triggers do nothing to allow this in a firearm. Despite this fact, the Biden administration decided to ban them via the regulatory power of the ATF.
However, the ATF doesn’t actually have the authority to up laws. It can only interpret and enforce laws passed by Congress, which makes its decisions here a tad questionable, at best.
Especially since they had to know this would land in court, which it has. A previous case resulted in an injunction.