Immigration and administration lawyers on Monday battled over whether President Donald Trump can use an 18th century wartime act against a Venezuelan gang in a case that is likely to ultimately be decided by the U.S. Supreme Court.

The attorneys sparred before a three-judge panel of the 5th Circuit Court of Appeals in New Orleans, the latest step in a tangled legal battle over Trump’s March invocation of the Alien Enemies Act of 1798 against the Tren de Aragua gang.

The law has only previously been used during World Wars I and II and the War of 1812. ACLU attorney Lee Gelernt told the three-judge panel that Trump’s use of it is inappropriate. “This has only been invoked three times in major, major wars, and now it’s being invoked in connection with a gang,” Gelernt said.

Deputy Assistant Attorney General Drew Ensign, arguing for the administration, said that courts cannot second-guess a president’s determination that the U.S. faces a threat from abroad and requires extraordinary measures to protect itself. He noted that the only time the high court weighed in on the act was in a case that dates from after fighting in Europe ended in World War II, when the court said it could not second-guess then-President Harry Truman’s assertion that suspected Nazis should still be held under the act because the war was still continuing.

“The president is due the utmost deference” in matters of foreign affairs and security, Ensign said.

Trump’s invocation has already been twice before the nation’s highest court on more technical issues. First, the court found that those accused of being TdA members deserved a “reasonable” amount of time to challenge that designation in court, but that their deportations could only be challenged in the locations they were held. That eliminated a national bar against deportations under the act issued by a federal judge in Washington, who later found the administration possibly committed contempt when it disregarded his orders and continued to fly some held under the AEA to a prison in El Salvador.

Then, after the ACLU and its allies began filing suits all around the country and winning rulings barring deportations under the measure, the high court stepped in a second time. In April it issued an unusual post-midnight ruling stopping the administration from deporting people from a slice of north Texas where there was yet no active ruling against removal.

As multiple lower court judges found the AEA couldn’t be used against a gang, the high court directed the 5th Circuit to consider the issue and how much time those held should have to challenge their designation.

The government, which initially provided minimal notice, now says the standard should be seven days to file an appeal. The ACLU argued for 30 days, the amount of time given to suspected Nazis held during World War II.

The panel that heard Monday’s arguments was comprised of one judge appointed by Trump, one by former President George W. Bush and one by Biden. Whatever it rules can be appealed to either the entire 5th circuit — one of the most conservative federal appeals courts in the country — or directly to the high court.

Trump has argued that TdA is acting at the behest of Venezuela’s government. The Act allows its use to combat either an “invasion” or a “predatory incursion.”

But the ACLU argues that the connection between the gang and the Venezuelan government is tangential at best, and that an assessment by 17 different intelligence agencies found little coordination between TdA and the government in Caracas. Gelernt contended that, by the standards laid out by the administration, the AEA could have been used against the mafia or any other criminal organization with tangential ties to other countries that has operated in the United States over the past 200 years.