The American Civil Liberties Union asked the U.S. Supreme Court to reject the Trump administration's position that undocumented immigrants who have re-entered the United States can be detained indefinitely, even when their deportation is far from certain.

In an amicus brief, the nonprofit told the justices that it has "serious due process concerns" when undocumented immigrants are denied bond hearings despite their claims of persecution or torture pending before an immigration judge.

"To lock up a human being without any opportunity for him or her to rebut the government's case is as basic a violation of due process as they come," the group wrote on Tuesday. "Where there is no evidence that an individual would flee or pose any danger to the community while she awaits her immigration hearing, detention is by definition arbitrary and violates due process."

The case, which the Supreme Court is poised to hear this term, concerns a group of immigrants from Honduras and El Salvador who were previously deported from the United States. After unlawfully re-entering, the government detained them, and their previous removal orders were automatically reinstated, according to their Supreme Court brief.

The government has argued that the plaintiffs' reinstated removal orders triggered a separate section of the Immigration and Nationality Act requiring detention when they might otherwise receive bond hearings.

The immigrants have said that section of the law should not apply because they are seeking new protections based on fears of persecution should they be re-deported to their home countries.

Because these fears are still being evaluated by an immigration judge, the plaintiffs should not be treated as other immigrants on the cusp of deportation, they argued.

The ACLU said that applying the mandatory-detention provisions, as per the government's position, could result in indefinite imprisonment. Withholding-of-removal proceedings can leave immigrants "subject to detention for months or even years," the group said.

"This Court has long held that the due process touchstone for any civil detention is an individualized hearing, before a neutral decisionmaker, to determine whether the person's imprisonment is justified," it added. "The same principle applies here."

But the government said that, even if these withholding claims succeed, it still retains the right to deport the group of immigrants to other countries that will accept them. Because deportation is still on the table regardless of the status of those claims, the administration argued, the group of immigrants should be treated identically to those who are about to be deported.

The ACLU rebutted that argument, saying that such third-country deportations are exceedingly rare.

Because of this, the ACLU said the availability of a third-country option should not mean the deportation-ready provision of the law kicks in. According to the American Immigration Council, fewer than 2% of immigrants who received persecution-based relief in fiscal year 2017 were ultimately deported to a third country.

The Justice Department also raised the possibility that having to scrutinize the practical odds of removal from immigrant to immigrant would be "patently unworkable."

"A case-by-case approach … would needlessly add to the burdens that are already 'overwhelming our immigration system,'" the department said, quoting a prior case.

But a coalition of former immigration trial and appeals judges pushed back on that idea with their own amicus brief Thursday.

"Bond hearings in withholding of removal proceedings are no different than bond hearings in other contexts," the group, representing 34 judges who have cumulatively overseen thousands of cases, wrote. "Contrary to [the administration's] assertion, bond hearings in withholding of removal proceedings neither lead to a slowdown of cases that 'thwart Congress' objectives' in enacting the immigration laws, nor impose an administrative burden on immigration courts."

The American Civil Liberties Union is represented by its own Michael Tan, Omar Jadwat, Judy Rabinovitz, Cecillia Wang and David D. Cole.

The coalition of former judges is represented by David Keyko, Robert Sills, Matthew Putorti, Daryl Kleiman, Patricia Rothenberg and Roland Reimers of Pillsbury Winthrop Shaw Pittman LLP.

The plaintiffs are represented by Paul Hughes, Michael Kimberly and Andrew Lyons-Berg of McDermott Will & Emery LLP, Simon Sandoval-Moshenberg and Rachel McFarland of the Legal Aid Justice Center, Mark Stevens of Murray Osorio PLLC, and Eugene Fidell of Yale Law School's Supreme Court Clinic.

The Trump administration is represented by Noel Francisco, Jeffrey Wall, Edwin Kneedler and Vivek Suri of the U.S. Solicitor General's Office and Lauren Fascett, Brian Ward and Joseph Hunt of the U.S. Department of Justice's Civil Division.

The case is Tony H. Pham et al. v. Maria Angelica Guzman Chavez et al., case number 19-897, at the U.S. Supreme Court.

--Editing by Michael Watanabe.