Philadelphia Mayor Michael Nutter has publicly signed an executive order that the city will no longer keep immigrants in police custody at the request of Immigration and Customs Enforcement or ICE.

The Wednesday announcement makes Philadelphia the latest city in the country to limit cooperation with federal officials.

After months of lobbying by immigrant advocates, Nutter has decided the city will no longer honor  ICE one-page detainers, which ask police to hold onto someone until that individual can be transferred to federal custody -- except when requests for violent offenders are backed by a formal warrant.

"The Philadelphia Police Department relies on information gathered from residents to solve crimes each and every day," Nutter said. "We do that in order to protect the safety of our communities. And without a significant level of trust and faith, citizens or others who are here just won't talk to law enforcement authorities."

The language of Nutter's executive order, said Kate Desormeau with the American Civil Liberties Union, "references Fourth Amendment rules that ICE has been flouting for decades."

However, immigration attorneys say there are no judicial warrants for immigration violations and so, practically, the order cuts one of the last ties between Philadelphia police and immigration enforcement, a process that began when the city stopped turning over victim and witness information a few years ago. Ultimately, it will mean fewer people picked up on local charges will be deported.

Maria Serna of the Latino advocacy organization Juntos said the new policy will improve relations between the immigrant community and police.

"Our communities live every day in fear, you know, because every encounter with the police [could mean going] to immigration and your deportation," she said. "And when this happens, the family is torn apart."

Philadelphia's only Latino City Council member, Maria Quinones-Sanchez, became emotional while talking about the executive order.

"This victory is so huge, not only for the city of Philadelphia but for rest of the country," she said. "And for those of you who do immigrant work and know the faces behind the stories, the people who have suffered who we couldn't save before."

ICE said it would continue to lodge detainers.

"The release of serious criminal offenders to the streets in a community, rather than to ICE custody, undermines ICE's ability to protect public safety and impedes us from enforcing the nation's immigration laws," said spokeswoman Nicole Navas.