Just a day before it was set to take effect, a federal judge called the legality of President Joe Biden’s new rule aimed at forcing private gun sellers to obtain federal licenses into question.

US District Judge Matthew Kacsmaryk issued a temporary restraining order (TRO) on Sunday, preventing the ATF from enforcing the new rule in Texas and against the members of multiple gun rights groups. He determined that the rule likely violated the Administrative Procedures Act because it contradicted the federal statute it was based on and reversed the agency’s previous interpretation.

“Plaintiffs understandably fear that these presumptions will trigger civil or criminal penalties for conduct deemed lawful just yesterday,” Kacsmaryk wrote in Texas v. ATF. “And as this Court’s analysis makes clear, Defendants’ Final Rule is almost certainly violative of — at the least — the [Administrative Procedure Act]. As such, ‘both the balance of equities and the public interest weigh in favor of allowing orderly judicial review of the Rule before anyone shuts down their businesses or sends them to jail.'”

The ruling pours cold water over the Biden administration’s final rollout of the new rule, which took effect for the rest of the country on Monday. It casts early doubt on the long-term viability of President Biden’s attempt to use administrative rulemaking to “move the U.S. as close to universal background checks as possible”—a policy goal he’s been unable to achieve via Congressional action.

The ATF finalized the rule in April. It expands who needs to obtain a Federal Firearms License (FFL) and thus conduct background checks before selling used guns on the secondhand market. The Biden administration pursued it following a tweak made to the definition of who is “engaged in the business” of firearms dealing in the 2022 Bipartisan Safer Communities Act (BSCA).

According to the ATF, the new rule applies primarily to persons who repeatedly sell firearms to “predominantly earn a profit.” However, it left unclear the exact number of sales that would trigger the rule, including by stipulating that “a single firearm transaction or offer to engage in a transaction” could require a license. The agency estimated more than 25,000 people have been selling firearms in violation of the standards outlined under the regulation, which now carries penalties of up to $250,000 in fines and five years in federal prison.

Republican-led states Texas, Louisiana, Mississippi, and Utah partnered with gun-rights groups Gun Owners of America, the Tennessee Firearms Association, and the Virginia Citizens Defense League to sue the ATF over the rule earlier this month.

Kacsmaryk found that Louisiana, Mississippi, and Utah lacked standing to challenge the rule. However, he said all the other plaintiffs demonstrated that they would be harmed financially or by the risk of prosecution if he allowed the ATF to enforce the rule against them. He also held that the rule’s lack of a minimum threshold for triggering licensing requirements and lack of exemption for people who buy or sell firearms for personal protection contradicted language in the BSCA.

“Nothing in the foregoing text suggests that the term’ personal collection’ does not include firearms accumulated primarily for personal protection — yet that is exactly what the Final Rule asserts,” Kacsmaryk wrote. “Defendants maintain their interpretation despite knowing that ‘two-thirds of Americans report owning firearms primarily for ‘defense’ or ‘protection’ — thereby necessitating the absurdity that the statute’s safe harbor provision provides no safe harbor at all for the majority of gun owners.”

Kacsmaryk’s ruling drew praise from Texas officials.

“I am relieved that we were able to secure a restraining order that will prevent this illegal rule from taking effect,” Texas Attorney General Ken Paxton (R.) said in a statement. “The Biden Administration cannot unilaterally overturn Americans’ constitutional rights and nullify the Second Amendment.”

The Department of Justice did not respond to a request for comment on the ruling. Gun-control advocates, meanwhile, criticized it as a public safety risk.

“The District Court’s decision to prevent ATF’s ‘Engaged in the Business Rule’ from taking full and immediate effect everywhere is not only deeply flawed, it’s also dangerous, and will put communities and law enforcement at greater risk of gun violence,” Eric Tirschwell, executive director of Everytown for Gun Safety’s legal arm, said in a press release.

The TRO halts the implementation of the new rule until June 2.