A judge late Wednesday blocked the Trump administration’s plans to resume federal executions next month, determining that the Justice Department’s proposed lethal injection procedure “is not authorized” by federal law.

The order at least temporarily calls off four executions scheduled for December and January, which would have been the first carried out by the federal government since 2003. The Justice Department filed a notice Thursday that it intends to appeal and filed a request to stay the judge’s injunction.

This escalating court battle over the federal death penalty comes as the Trump administration is forcefully countering national trends in capital punishment, scheduling multiple lethal injections at a time when executions have been declining.

In her order, U.S. District Judge Tanya Chutkan of the District of Columbia wrote that she was issuing a preliminary injunction to prevent the inmates’ executions while their legal challenges play out after concluding they were likely to succeed in arguing that the new lethal injection procedure “exceeds statutory authority.”

When the Justice Department announced in July that it would resume executions, the department also said Attorney General William Barr had ordered officials to adopt a new lethal injection protocol using a single drug – pentobarbital – rather than the three-drug combination previously in place.

Chutkan, who was nominated by President Barack Obama, wrote that creating a single procedure for all federal executions “very likely exceeds the authority provided by the” Federal Death Penalty Act. She wrote that under that act, federal executions must be carried out “in the manner prescribed by the law of the State in which the sentence is imposed.”

Lethal injection is the primary method of execution in the United States, but specific protocols – including the type and number of drugs – vary from state to state.

States across the country have scrambled their lethal injection procedures and struggled to find drugs in recent years amid significant pushback from pharmaceutical firms opposing the use of their products in executions. Some states have rewritten their lethal injection procedures multiple times, while others have turned to different execution methods including a firing squad and nitrogen gas.

When the federal protocol was announced, the Justice Department noted that it echoed the practices used by Texas, Georgia and Missouri. All three have shifted from three-drug procedures to using only pentobarbital, according to the Death Penalty Information Center, and they are among the country’s most active states for capital punishment.

Two of the death-row inmates in the case were convicted in Texas and Missouri, both of which use pentobarbital for executions. Another was convicted in Indiana. The fourth was convicted in Iowa, which has no death penalty. In such cases, Chutkan noted, the Federal Death Penalty Act says a court must pick a death penalty state. In the Iowa case, the courts chose Indiana, the state where federal executions are carried out. That state has a three-drug lethal injection protocol.

The death-row inmates had shown that without an injunction, “they will suffer the irreparable harm of being executed under a potentially unlawful procedure before their claims can be fully adjudicated,” Chutkan wrote.

While the federal government argued it could be harmed by delaying the executions, Chutkan wrote that “the public is not served by short-circuiting legitimate judicial process, and is greatly served by attempting to ensure that the most serious punishment is imposed lawfully.”

When Barr announced the executions, he said officials “owe it to the victims and their families to carry forward the sentence imposed by our justice system.”

In its motion to stay the injunction Thursday, the Justice Department argued that, under Chutkan’s interpretation of the Federal Death Penalty Act, the federal government would be expected “to follow procedures in the nearly 30 distinct lethal execution protocols used by the States” rather than simply using lethal injection in places where that is on the books.

When the federal act was passed, the department continues, at least a dozen states had adopted lethal injection with varying procedures.

“It is inconceivable,” the department writes, that lawmakers meant for federal officials to mimic “all of those procedures in spite of the infinite number of variables,” including things like the number of syringes and amounts of saline flush.

A spokesman for the Justice Department declined to comment Thursday. Barr told the Associated Press he would take the case to the Supreme Court if the judge’s order stands.

The department also wrote in its stay request that it “has mobilized its resources to carry out the lawful sentence,” filing a declaration from Rick Winter, a regional counsel for the Bureau of Prisons, that discussed some of the arrangements the agency has begun making for executions.

Shawn Nolan, an attorney for some of the inmates, said the government was “trying to do an end-run around litigation” when it set the execution dates and announced a new protocol. He said they had expected the government to appeal.

“We are hopeful the judge’s very thoughtful and well-reasoned opinion will stand up on appeal,” Nolan said in an interview.

Chutkan’s decision “was decided on straightforward grounds,” said Robert Dunham, director of the Death Penalty Information Center.

“There is a federal statute. The language of the statute is clear. What the attorney general did exceeded the language of the statute,” Dunham said.

The planned executions have stirred controversy and drawn opposition from at least some relatives linked to the cases.

Daniel Lewis Lee, the first person who was scheduled to be executed, killed a family of three, including 8-year-old Sarah Powell and her mother, Nancy Mueller, according to the Justice Department. Mueller’s mother, Earlene Peterson, has asked the Trump administration to call off the execution, as have some of their other relatives. They have argued instead for a sentence of life without parole.

Their pleas were echoed by statements signed recently by hundreds of other murder victims’ relatives, current and former law enforcement officials and former judges and corrections officials, all of whom asked the department to stop the planned executions.

A fifth federal execution also announced in July was stayed by a different court last month.