Six minor plaintiffs in the lawsuit—which adds a new twist to an ongoing battle over migrant families—are now with parents and held in family detention in Texas. During their period of separation, some of their parents failed to pass so-called “credible fear” asylum interviews and some signed forms that put families in a pipeline toward deportation.

Pro bono lawyers with the firm Hogan Lovells argue in a lawsuit filed in U.S. District Court in Washington D.C. on Monday that parents who signed these forms did so under duress and without understanding the documents.

“They basically gave the parents a Hobson’s choice,” said T. Clark Weymouth, one of the minor plaintiffs’ attorneys, speaking of U.S. officials. If they didn’t sign the forms, some parents thought they wouldn’t see their children again, he said.

Weymouth and other attorneys argue that U.S. Department of Homeland Security officials “intend to embark on a policy of immediately deporting reunified families in which one of the parents has been given an expedited removal order, without honoring the minor children’s individually vested rights to seek asylum.”