In response to 2017's mass shooting in Las Vegas, President Donald Trump vowed to use executive authority to ban bump stocks, a type of firearms accessory that the shooter reportedly used. The Justice Department soon delivered on Trump's promise with a new rule amending "the Bureau of Alcohol, Tobacco, Firearms and Explosives regulations to clarify that [bump-stock-type devices] are 'machineguns' as defined by the National Firearms Act of 1934 and the Gun Control Act of 1968" because "such devices allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger." In effect, the Trump administration rewrote federal gun law in order to achieve the president's preferred policy outcome.

That unilateral executive action has now come under blistering criticism from two federal judges appointed by Trump himself.

On March 2, Supreme Court Justice Neil Gorsuch issued a statement respecting the denial of certiorari in Guedes v. Bureau of Alcohol, Tobacco, Firearms and Explosives. The executive branch "used to tell everyone that bump stocks don't qualify as 'machineguns.' Now it says the opposite." Yet "the law hasn't changed, only an agency's interpretation of it," Gorsuch complained. "How, in all of this, can ordinary citizens be expected to keep up—required not only to conform their conduct to the fairest reading of the law they might expect from a neutral judge, but forced to guess whether the statute will be declared ambiguous….And why should courts, charged with the independent and neutral interpretation of the laws Congress has enacted, defer to such bureaucratic pirouetting?"

Gorsuch just got some company. This week, Judge Brantley Starr, a Trump appointee who sits on the U.S. District Court for the Northern District of Texas, issued an opinion in Lane v. United States that basically accused the Justice Department of ignoring basic principles of constitutional governance in its defense of the Trump administration's bump stock ban.

The Justice Department justified the ban as a lawful exercise of the federal police power, Judge Starr observed. But "the federal government forgot the Tenth Amendment and the structure of the Constitution itself," which grants no such power to the feds. "It is concerning that the federal government believes it swallowed the states whole. Assuming the federal government didn't abolish the states to take their police power," Starr wrote, he had no choice but to deny the government's motion to dismiss the case. He then tartly added: "The Court will allow the government to try again and explain which enumerated power justifies the federal regulation."

To say the least, Trump's bump stock ban is not off to a winning start in federal court.