The Obama administration is facing its latest challenge on immigration enforcement -- but this time, it is from an ally.

Chicago Mayor Rahm Emanuel, who as White House Chief of Staff was a prominent member of the president's inner circle, proposed on Tuesday a measure that would prohibit police officers from turning undocumented immigrants over to federal authorities if the immigrants had not committed crimes.

The administration has tangled with Republican-controlled states over a raft of tough new immigration laws emulating Arizona's controversial SB 1070. That legal battle recently reached the Supreme Court, which in striking down sections of Arizona's law partially affirmed the federal government's control over immigration policy.

But where Arizona's law and copycat measures in Georgia, South Carolina and Alabama sought to tighten enforcement, Emanuel is taking the opposite approach. Liberal critics and immigration advocates have assailed the Obama administration for pushing deportations to record levels -- more than 1.2 million so far -- contending that in the process, the government has deported many immigrants who pose no threat to society.

Emanuel pushed back on Tuesday, saying he wanted to make Chicago the most immigrant-friendly country in the city.

If you have no criminal record, being part of a community is not a problem for you, Emanuel said. We want to welcome you to the city of Chicago. 

The move is reminiscent of an attempt last year by Illinois Governor Pat Quinn, also a Democrat, to opt out of a federal immigration enforcement mechanism known as Secure Communities. The program requires state and local law enforcement to enter the fingerprints of people they arrest into a federal database, allowing authorities to identify deportable immigrants.

Three Democratic governors tried to pull their states from the program, a Bush-era holdover that Obama embraced and expanded. They said it fractured families, bred distrust between communities and police officers and undercut the Obama administration's promise to focus on deporting immigrants who had committed serious crimes or repeatedly broken immigration laws. The administration overrode those concerns and ordered the program's implementation.

In the past year, the administration has sought to recalibrate its immigration enforcement practices. Officials unveiled new guidelines last summer that ordered Immigration and Customs Enforcement personnel to emphasize criminal immigrants and allowed some other undocumented immigrants to have pending deportation cases suspended. More recently, the administration announced it would stop deporting young undocumented immigrants who arrived in the country as children and have stayed out of trouble.