Former President Donald Trump's controversial ban on bump stocks was placed on hold last week by a federal appeals court that determined the ban is probably unconstitutional.

What is the background?

After the Las Vegas massacre — in which one gunman murdered 61 people and injured more than 400 others attending a country music festival — Trump vowed to take action to prevent another mass killing like that from happening again.

Trump zeroed in on bump stocks, a device the Las Vegas killer used to quickly murder so many people. A bump stock uses the recoil of a semi-automatic rifle to rapidly fire ammunition. The device itself does not modify a rifle's firing capacity — a rifle modified with a bump stock still requires the trigger to be depressed to fire every round — but allows the trigger to be depressed so rapidly that it essentially fires similarly to a fully automatic rifle.

More than one year after the Las Vegas massacre, the Justice Department issued a new Bureau of Alcohol, Tobacco, Firearms, and Explosives regulation updating the definition of "machine gun" to include firearms modified with bump stocks.

The Justice Department claimed such firearms are machine guns because they "allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger. Specifically, these devices convert an otherwise semiautomatic firearm into a machine gun ..."

What did the court rule?

The group Gun Owners of America and others sued the government, arguing the bump stock ban violated the Fifth Amendment's takings clause, the 14th Amendment's right to due process, and the Administrative Procedure Act, according to Bloomberg Law.

The Sixth Circuit Court of Appeals ruled Thursday that a federal district court should have granted the plaintiffs' request for a preliminary injunction against the ban because they could likely prove the ban is unlawful.

The federal government argued the bump stock ban is justified under the Chevron deference, a legal doctrine permitting judicial deference to an agency's statutory interpretation of ambiguous law.

However, the appeals court vehemently disagreed.

"[The] Chevron deference categorically does not apply to the judicial interpretation of statutes that criminalize conduct," the court explained. "Because the definition of machine gun...applies to a machine-gun ban carrying criminal culpability and penalties, we cannot grant Chevron deference to the ATF's interpretation."

In fact, the court explained the question of bump stock lawfulness should be answered — but not by unaccountable executives.

Whether ownership of a bump-stock device should be criminally punished is a question for our society. Indeed, the Las Vegas shooting sparked an intense national debate on the benefits and risks of bump-stock ownership. And because criminal laws are rooted in the community, the people determine for themselves—through their legislators—what is right or wrong. The executive enforces those determinations. It is not the role of the executive— particularly the unelected administrative state—to dictate to the public what is right and what is wrong.

But the court did not stop there.

Not only is the ban not defensible under judicial precedent, but the court rejected the government's attempt to redefine "machine gun," ruling that "bump stock does not fall within the statutory definition of a machine gun."

Will the Supreme Court hear the case?

While the appeals court ultimately remanded the case to the lower court, the Supreme Court has already signaled unwillingness to address the issue.

In fact, the Supreme Court last year rejected hearing a similar case, Guedes v. ATF. Justice Neil Gorsuch essentially explained at the time that lower courts needed to resolve issues with the case before the Supreme Court reviewed it.