Posted by 
The six Republican justices handed down a decision on Friday that effectively legalizes civilian ownership of automatic weapons. All three of the Court’s Democrats dissented.
The Court’s decision in Garland v. Cargill involves bump stocks, devices that allow ordinary semiautomatic weapons that can legally be owned by civilians to automatically fire, much like a machine gun designed for that purpose. Bump stocks cause a semiautomatic gun’s trigger to buck against the shooter’s finger, repeatedly “bumping” the trigger and making the gun rapidly fire.
A semiautomatic weapon refers to a gun that loads a bullet into the chamber or otherwise prepares itself to fire again after discharging a bullet, but that will not fire a second bullet until the shooter pulls the trigger a second time. An automatic weapon, by contrast, will fire a continuous stream of bullets.
As Justice Sonia Sotomayor notes in her dissent, the Trump administration decided to ban bump stocks after a shooter opened fire on a music festival in Las Vegas in 2017, killing 58 people and wounding over 500 in a matter of minutes. The shooter used bump stocks to kill so many people so quickly.
A 1986 law makes it a crime to own a “machinegun,” and the Trump administration determined that this law is broad enough to encompass bump stocks. That law defines a “machinegun” to include “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.”
This law is, in fairness, rather ambiguous. And lower courts divided on whether it could be read as the Trump administration read it.
Some courts concluded that the phrase “a single function of the trigger” should be read to mean, as one of those courts put it, “a single pull of the trigger from the perspective of the shooter.” Thus, a semiautomatic weapon equipped with a bump stock counts as a machine gun because “the shooter engages in a single pull of the trigger with her trigger finger, and that action, via the operation of the bump stock, yields a continuous stream of fire as long she keeps her finger stationary and does not release it.”
Writing for the Court’s Democratic minority, Sotomayor adopts this reading of the statute. In her words, “a machinegun does not fire itself. The important question under the statute is how a person can fire it.”
The other plausible reading of the statute focuses on whether the trigger itself moves back and forth each time a bullet is fired. Writing for the Court’s Republicans, Justice Clarence Thomas adopts this view, arguing that “all that a bump stock does is accelerate the rate of fire by causing these distinct ‘function[s]’ of the trigger to occur in rapid succession.”
Both of these outcomes can also be supported by competing rules guiding how statutes should be interpreted.
Though Thomas did not rely on this rule in his opinion, some lower courts applied the “rule of lenity” to justify ruling in favor of bump stocks. Generally, this rule establishes that, when a criminal law is ambiguous, the ambiguity should be resolved in favor of the defendants.
Alternatively, a rule known as the “presumption against ineffectiveness” cuts in the other direction. As the Supreme Court said in The Emily and the Caroline (1824), courts should avoid reading laws in ways that would render “the law in a great measure nugatory and enable offenders to elude its provisions in the most easy manner.” (“Nugatory” means that the law is inoperative or unable to function.)
Sotomayor argues in her opinion that this presumption against ineffectiveness favors her reading of the statute, because Thomas’s reading would effectively nullify the ban on machine guns. As she writes, “anyone shooting a bump-stock-equipped AR–15 can fire at a rate between 400 and 800 rounds per minute with a single pull of the trigger.”
So who is correct here? The honest answer is that both possible readings of the statute are equally permissible, which explains why the lower courts divided. What the Court’s decision in Cargill exposes is that not every statutory interpretation question has a clear answer, and judges can often pick the outcome that they want.
And so the six Republicans — members of a political party that typically supports gun rights, despite the Trump administration’s actions on bump stocks — picked the outcome that aligns with their political party’s pro-gun stance. The justices who belong to the Democratic Party, meanwhile, picked the outcome that aligns with their party’s position on guns.
