Migrants and advocacy groups have fired back at the federal government's bid to overturn the Ninth Circuit's block on a policy that makes asylum-seekers wait in Mexico, telling the U.S. Supreme Court that the COVID-19 pandemic made the case moot.

The groups, which include the Innovation Law Lab, a migrant advocacy collective, and 11 migrants seeking to remain in the U.S. while they wait for their asylum applications to be processed, asked the court Wednesday not to waste time by taking up the Ninth Circuit decision that found the Trump administration's Migrant Protection Protocols to be in violation of the Immigration and Nationality Act.

Unlawful or not, they said, an order from the Centers for Disease Control and Prevention closing the border has effectively replaced it.

"The [CDC] order, which is intended to remain in effect for as long as the public health concerns raised by COVID-19 persist, renders MPP effectively superfluous as a border enforcement tool, and the government has largely abandoned its use for the processing of new arrivals," they argued in a brief.

The CDC did not respond to a request for comment Thursday.

According to a U.S. Department of Homeland Security report published in October 2019, the department had conducted more than 7,400 credible fear interviews -- which exempts migrants from having to wait in Mexico if they can show they may be subject to persecution or torture there -- and fewer than 1,000 of those screenings had a positive result. That number is "unsurprising," DHS said, explaining that those "amenable to MPP voluntarily entered Mexico en route to the United States."

By refusing the government's petition for the high court's review, justices could leave the question open to future cases that may be better positioned to address the full scope of the policy, which has impacted tens of thousands of migrants seeking asylum at the southern U.S. border, the migrants and advocacy groups said.

While the Ninth Circuit's ruling only requires the government to bring back the 11 migrants named in the case, better test cases are "already in the pipeline," they said.

Attorneys for the Innovation Law Lab declined to comment.

The government is represented by Jeffrey B. Wall, Edwin S. Kneedler, Michael R. Huston and Austin L. Raynor of the U.S. Solicitor General's Office and Scott G. Stewart, Erez Reuveni and Archith Ramkumar of the U.S. Department of Justice's Civil Division.

The asylum-seekers and organizations are represented by Judy Rabinovitz, Michael Tan, Omar Jadwat, Lee Gelernt, Anand Balakrishnan, Daniel Galindo, Jennifer Chang Newell, Katrina Eiland, Cody Wofsy, Julie Veroff, Sean Riordan, Christine P. Sun and Steven Watt of the ACLU, Melissa Crow, Mary Bauer, Gracie Willis and Mich P. Gonzalez of the Southern Poverty Law Center and Blaine Bookey, Karen Musalo, Eunice Lee, Kathryn Jastram and Sayoni Maitra of the Center for Gender and Refugee Studies.

The case is Wolf et al. v. Innovation Law Lab et al., case number 19-1212, in the Supreme Court of the United States.

--Additional reporting by Sarah Martinson. Editing by Jill Coffey.

Correction: A previous version of this article misconstrued the data on DHS' credible fear screenings. The error has been corrected.