As Donald Trump continues to escalate his attacks on a federal judge who has challenged whether his administration’s deportations defied a court order last week, a federal appeals court on Monday will hear arguments for the first time about the president’s invocation of the Alien Enemies Act to deport more than two hundred Venezuelan migrants who the administration alleges are members of the Tren de Aragua gang.

If the D.C. Circuit Court of Appeals overturns a lower court’s order blocking the president’s recent use of the centuries-old wartime law, the Trump administration could exercise the authority to deport any suspected migrant gang member with little-to-no due process.

While the Trump administration has argued that Tren de Aragua is a “hybrid criminal state” invading the U.S., lawyers representing the Venezuelan men targeted under Trump’s proclamation have argued that the president exceeded his authority by using the Alien Enemies Act against a gang — rather than a state actor — outside of wartime.

“The President is trying to write Congress’s limits out of the act,” the plaintiffs argued, adding that U.S. presidents have used the law three other times during or immediately preceding a war.

But the Trump administration has argued that the judiciary does not have the right to review the use of the Alien Enemies Act, alleging the deportations fall under the president’s Article II powers to remove alleged terrorists and execute the country’s foreign policy.

“The President’s action is lawful and based upon a long history of using war authorities against organizations connected to foreign states and national security judgments, which are not subject to judicial second guessing,” DOJ lawyers have argued in court filings.

Last week, U.S. District Judge James Boasberg temporarily blocked the president’s use of the law to deport more than two hundred alleged gang members with no due process, calling the removals “awfully frightening” and “incredibly troublesome.” An official with the U.S. Immigration and Customs Enforcement subsequently acknowledged in a sworn declaration that “many” of the noncitizens deported last wekend under the Alien Enemies Act did not have criminal records in the United States.

The Trump administration is asking the appeals court to overturn Boasberg’s temporary restraining order blocking the deportations, while Judge Boasberg continues to examine whether the Trump administration deliberately defied his order by sending the men to an El Salvadoran prison rather than returning them to the United States as he directed.

“The government’s not being terribly cooperative at this point, but I will get to the bottom of whether they violated my order and who ordered this and what’s the consequence,” Boasberg said on Friday.

With deportations under the Alien Enemies Act temporarily blocked, the Trump administration has vowed to use other authorities to deport noncitizens. Over the weekend, Venezuelan National Assembly President Jorge Rodriguez announced that the country had reached an agreement to resume repatriation flights of Venezuelan migrants from the U.S.

“We’re going to keep targeting the worst of the worst, which we’ve been doing since day one, and deporting from the United States through the various laws on the books,” border czar Tom Homan told ABC’s Jon Karl on Sunday.

The three-person panel hearing today’s arguments includes two judges nominated by Republican presidents, including one nominated by Trump himself. The D.C. Circuit is the last stop before the Trump administration could take the case to the U.S. Supreme Court, where Trump nominated three judges during his last term, solidifying the court’s conservative majority.