The Department of Justice plans to appeal.
"We are disappointed that the court continues to refuse to end a long-standing and unnecessary injunction," said Department of Homeland Security spokesman Russ Knocke. "The civil war in El Salvador ended several years ago. Circumstances there that were the basis for the injunction no longer exist."
Among other things, the injunction requires immigration authorities to advise Salvadorans of their right to apply for political asylum. It was issued after Salvadoran refugees accused immigration officials of using threats and coercion to discourage them from applying.
In 2005, the Justice Department filed a motion seeking to dissolve the injunction, arguing the protections got in the way of current "expedited removal" policy that allows Immigration and Customs Enforcement to deport certain illegal immigrants without hearings. The government said it had adopted procedures to ensure detainees wouldn't be coerced into giving up their rights.
Morrow, however, wrote that authorities don't always follow those regulations.
She cited one study showing fewer than 10 percent of immigrants at the San Ysidro port of entry in Southern California were advised of their rights for asylum.
She also said evidence showed some detention centers lacked computers or had outdated or missing legal materials. At others, phones were out of service for long periods of time or the calls were cut off abruptly.
The court also found that despite the end of the civil war in El Salvador, immigrants from there continue to have legitimate asylum claims.
The National Immigration Law Center and the ACLU of Southern California opposed the government's request to end the injunction.