Immigration advocates hailed a court ruling on July 24 that could mean the end of an Immigration and Customs Enforcement policy to lock up families in compounds run by for-profit prison companies while they pursue asylum and other types of protection from deportation.

Judge Dolly Gee of the Central California District Court found that I.C.E.’s strategy—enacted last summer—of detaining women and their children as a deterrent to others who might try to cross the U.S.-Mexico border violated a court settlement reached in 1997. In her ruling Gee said she found it “astonishing that the defendants have enacted a policy requiring such expensive infrastructure without more evidence to show that it would be compliant with an agreement that has been in effect for nearly 20 years or effective at achieving what defendants hoped it would accomplish.”

The U.S. Conference of Catholic Bishops and the Center for Migration Studies issued a scathing report in May based on bishops’ visits to two family detention centers in Texas. It decried conditions and recommended dismantling the whole system, replacing it with less drastic ways of keeping track of immigrants who are awaiting the outcome of legal cases.

Auxiliary Bishop Eusebio L. Elizondo of Seattle, chairman of the U.S.C.C.B. Committee on Migration, welcomed Gee’s ruling and urged the administration to comply quickly.

“Appealing the decision would only prolong a flawed and unjust policy of treating this vulnerable population as criminals,” he said in a statement released on July 27.

The National Immigrant Justice Center also urged the administration to comply immediately. “Rather than double down on a costly policy that has been plagued with problems, including suicide attempts, inadequate medical and mental health care, prolonged periods of detention, and extremely limited access to counsel, [the Department of Homeland Security] must use the least restrictive alternatives to detention to mitigate concerns about flight risk,” said a statement from the center.

More than 55,000 families were among a surge of Central American immigrants across the U.S.-Mexico border last summer. Along with 57,000 unaccompanied minors, the families were fleeing violence and other dangers in their home countries of El Salvador, Guatemala and Honduras.

Most of the families in the centers have met the first legal hurdle in applying for asylum. Of the tens of thousands of other families apprehended at the border, most have not been detained but were released on bond pending adjudication of their attempts to be allowed to remain. But some families have been held in the centers for more than a year.

The judge ruled that children who are picked up by the Border Patrol while traveling with their mothers should be treated with the same level of care as those who arrive on their own. She said I.C.E. failed to provide any evidence to support the agency’s argument that it was necessary to detain families as a deterrent. She ordered the administration to release children and parents unless there is a determination that there is “a significant flight risk, or a threat to others or the national security…which cannot be mitigated by an appropriate bond or conditions of release.”

She also ordered I.C.E. to come up with standards for conditions under which immigrant children, including those with their parents, are held in even temporary conditions. The conditions addressed by Gee’s order included frigid, overcrowded holding cells, inadequate medical care and other problems.