The judge ordered the government to immediately return Carmen and her daughter to the U.S. If the government does not fully comply with the order, the judge said he would order officials to appear in court to explain why they should not be held in contempt.
The woman - identified in court as Carmen - is a plaintiff in an ACLU lawsuit filed this week over efforts to prevent immigrants from seeking asylum due to domestic and gang violence in their home countries.
The suit also says asylum adjudicators are required to ignore federal appellate decisions that conflict with the new credible fear policies, "thus purporting to make the immigration authorities the ultimate arbiters of the law".
Sessions ruled in June that asylum is generally not available to people fleeing violence by private rather than government actors. By Thursday evening, the mother and her daughter had landed in El Salvador.
A DHS official told NPR on Friday, "In compliance with the court's order, upon arrival in El Salvador, the plaintiffs did not disembark and were promptly returned to the United States".
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"Carmen and her daughter are right now somewhere in the air between Texas and El Salvador", ACLU lead attorney in the case Jennifer Chang Newell told NBC. Some of Carmen's coworkers had already been murdered and her husband was abusive.
A "credible fear" interview is a threshold screening that determines whether there is a "significant possibility" that an immigrant could show they are eligible for asylum in a full hearing with evidence, witnesses, and appeals.
In June, the Trump administration determined that fleeing domestic violence and gang violence would no longer be accepted as a means for refuge in the United States. The case is part of an ongoing legal battle over asylum claims.
The lawsuit says Sessions's ruling, and updated guidelines for asylum officers that the Department of Homeland Security issued a month later, subject migrants in expedited removal proceedings to an "unlawful screening standard" that deprives them of their rights under federal law.
From there, Sessions has argued, asylum-seekers are typically released into the interior of the country while they await hearings, often years away.
Two of the children and their mothers were deported before the suit was filed; the rest were being detained in Texas and NY.