From Firearms Policy Coalition:

ATF has once again unlawfully and unconstitutionally exceeded its authority and changed the law by issuing a new determination that is devoid of logic and reason, contains no explanation as to the manner in which it arrived at its conclusion, conflicts with its prior determinations, and embodies the very essence of “arbitrary and capricious”. 
After examining a sample Q Honey Badger Pistol, the ATF’s Firearms and Ammunition Technology Division (FATD) concluded that “the objective features of the Honey Badger firearm, configured with the subject stabilizing brace, indicate the firearm is designed and intended to be fired from the shoulder.” FATD further concluded that it is a SBR as defined by the National Firearms Act (NFA) and Gun Control Act (GCA). Yet, ATF does not explain how it arrived at this conclusion other than vague generalizations that the firearm was “designed” to be fired from the shoulder and by virtue of its barrel length meeting the definition of a SBR.