A group of Republican-led states filed an emergency application Monday with the Supreme Court as part of a last-ditch effort to halt the lifting of Title 42, the federal order blocking millions of migrants from entering the U.S. on public health grounds.

The move to seek relief from the high court comes after a three-judge panel on the D.C. Circuit Court of Appeals on Friday rejected the states’ bid to suspend the policy’s expected termination. The Title 42 restriction is scheduled to wind down Wednesday, following a lower-court ruling that held the policy illegal. The appeals panel also denied the states’ request for a seven-day administrative stay, declaring the GOP states waited too long to step into the case over the legality of the Title 42 order, which began almost two years ago.

“Such a stay is particularly appropriate given the enormous harms that would otherwise be inflicted upon the States and further because there is not the slightest indication that DHS could ever meaningfully remedy those harms after they have occurred,” Louisiana Attorney General Jeff Landry and Arizona Attorney General Mark Brnovich wrote in the Monday’s filing, warning that the Department of Homeland Security estimates border crossings could double from 7,000 to 15,000 amid the policy’s end.

“Indeed, there has already been a surge of migrants approaching the border in anticipation of the December 21 stay expiration, underscoring the States’ harms,” Landry and Brnovich said.

It is not yet clear how the Supreme Court will respond, but if Chief Justice John Roberts agrees, he could grant a temporary stay — leaving Title 42 in place — while the justices consider whether to grant longer-term relief.

The legal uncertainty adds another layer to a chaotic week at the U.S.-Mexico border, as the Biden administration prepares to terminate the Trump implementation of a health policy used more than 2 million times at the border during the Covid pandemic to expel asylum-seeking migrants. Critics from both sides of the aisle have expressed doubt about the administration’s preparation.

The major policy shift is expected to inundate a southern border already strained by irregular migration and an overwhelmed asylum processing system. Already, thousands of migrants appeared to have gathered along the U.S.-Mexico border, knowing border officials will not be able to remove them as quickly as they could since Title 42 was reinstated in March 2020. The mayor of El Paso, Texas, declared a state of emergency over the weekend, citing concerns over the ability to handle the influx of people crossing into the United States.

Administration officials are still finalizing plans to deal with the impending surge, people familiar with the planning told POLITICO. DHS is weighing a revival of a “transit ban” model, ramping up new training for asylum officers to help them understand who qualifies under the international Convention Against Torture and considering an expansion of humanitarian parole programs for Haitians, Nicaraguans and Cubans.