The United States Supreme Court started its new session on Monday by declining to hear two cases challenging the bump stock ban: W. Clark Aposhian v. Attorney General Merrick Garland and Gun Owners of America v. Attorney General Merrick Garland.

In December 2018, shortly after the Las Vegas massacre, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) proposed a rule change so the definition of a “machinegun” would include “bump-stock-type devices.” The rule eventually went into effect in March of 2019.

The two cases the Supreme Court declined to hear are the latest in a string of court cases challenging the rule change.

In 2018, Firearms Policy Coalition (FPC), Firearms Policy Foundation (FPC), and the Madison Society Foundation (MSF), sought a preliminary injunction to prevent the rule change from going into effect. The goal was to prevent the rule change while the court reviewed the constitutionality of the rule change.

The judge at the time allowed bump stocks to be reclassified as “machineguns” because of the rule’s ambiguity:

Because both terms are ambiguous, ATF was permitted to reasonably interpret them, and in light of their ordinary meaning, it was reasonable for ATF to interpret “single function of the trigger” to mean “single pull of the trigger and analogous motions” and “automatically” to mean “as the result of a selfacting or self-regulating mechanism that allows the firing of multiple rounds through a single pull of the trigger.” ATF also reasonably applied these definitions when it concluded that bump stocks permit a shooter to discharge multiple rounds automatically with a single function of the trigger. That this decision marked a reversal of ATF’s previous interpretation is not a basis for invalidating the rule because ATF’s current interpretation is lawful and ATF adequately explained the change in interpretation.

Those caught in possession of a bump stock face a felony conviction, up to 10 years in prison, a $250,000 fine, or both prison time and a fine.