Supreme Court rules in favor of gun lobby position and voids ATF ruling that bump stocks should be controlled; Court technical justification drawn from gun lobby amicus curiae brief.

For context, the shooter in the October 1, 2017 mass shooting event in Las Vegas killed 58 people and wounded nearly six hundred in a ten minute rampage, achieving firing rates of nine rounds a second using bump stocks and numerous AR15 and AR10 firearms.

From Court decision: https://asecondamendmentfor21stcenturyamerica.org/s/602us1r36_k537-Cargill-wy3l.pdf

Held: ATF exceeded its statutory authority by issuing a Rule that classifies a bump stock as a “machine gun” under § 5845(b). Pp. 415–429. (a) A semiautomatic rife equipped with a bump stock is not a “machine gun” as defined by § 5845(b) because: (1) it cannot fire more than one shot “by a single function of the trigger” and (2) even if it could, it would not do so “automatically.” ATF therefore exceeded its statutory authority by issuing a Rule that classifies bump stocks as machine guns. P. 415. (b) A semiautomatic rife equipped with a bump stock does not fire more than one shot “by a single function of the trigger.” The phrase “function of the trigger” refers to the mode of action by which the trigger activates the firing mechanism. No one disputes that a semiautomatic rifle without a bump stock is not a machine gun because a shooter must release and reset the trigger between every shot. And, any subsequent shot fired after the trigger has been released and reset is the result of a separate and distinct “function of the trigger.” Nothing changes when a semiautomatic rife is equipped with a bump stock. Between every shot, the shooter must release pressure from the trigger and allow it to reset before reengaging the trigger for another shot. A bump stock merely reduces the amount of time that elapses between separate “functions” of the trigger.