This article is from the archive of our partner National Journal

Republicans are pressing the White House to crack down on "sanctuary cities"—but there's only so much the Obama administration could do, even if it wanted to.

Jeb Bush, Marco Rubio, and plenty of other 2016 candidates have called for new limits on sanctuary cities after a San Francisco woman was fatally shot this month, allegedly by an undocumented immigrant who had been deported from the U.S. five times.

"There are over 200 sanctuary cities and counties in this country, and the U.S. Department of Justice has done absolutely nothing—nothing!—to prevent this," former Texas Gov. Rick Perry said last weekend.

So far, none of the major cities that refuse to help enforce federal immigration laws, including San Francisco, have shown much interest in changing their policies. And legal experts say it's unclear exactly how much power the federal government has to force cities' hands—mostly because the Justice Department has never shown much interest in doing so.

There's no formal definition of a "sanctuary city." Generally, the term refers to localities that have said they won't use their own resources to help enforce federal immigration laws. Supporters say the approach makes their cities safer, in large part because it encourages undocumented immigrants to report crimes and cooperate with police, free from the threat of deportation.

But in the wake of the San Francisco shooting, congressional Republicans have called on the Justice Department to crack down on local nonenforcement, and have offered their own proposals to force cities to cooperate with Immigration and Customs Enforcement.

One proposal, from Sen. Tom Cotton, would withhold Homeland Security grants from any city where official policy "prohibits law enforcement officers "¦ from assisting or cooperating with federal immigration law enforcement in the course of carrying out the officers' routine law enforcement duties."

Cutting off federal funds to cities that won't help with immigration enforcement—the approach Bush also has endorsed—would probably be the most effective way to eliminate "sanctuary cities," said Huyen Pham, a law professor at Texas A&M University who specializes in immigration law.

The types of policies singled out in Cotton's proposal already are illegal. Two federal laws, passed in 1996, say that states and cities can't pass their own laws prohibiting local officials from sharing information with federal immigration officials.

But hundreds of cities have tried to work around those limits, and the federal government has made "surprisingly" few attempts to stop them, Pham said. That reluctance to challenge local policies, she noted, spans the Obama and George W. Bush administrations.

Several cities, for example, won't use local resources to determine residents' immigration status. So, while it's illegal for them to refuse to share citizenship information with ICE, they simply don't collect that information in the first place—meaning they have nothing to share.

"Though this method does not directly conflict with federal requirements that states and localities permit the free exchange of information regarding persons' immigration status, it results in specified agencies or officers lacking any information about persons' immigration status that they could share with federal authorities," the Congressional Research Service said in a 2009 report.

San Francisco's noncooperation policy is considered one of the most aggressive in the country. It bars local officials from helping to enforce federal immigration laws "unless such assistance is required by federal or state statute, regulation, or court decision"—and ICE has consistently clashed with the city over whether it complies with federal law.

San Francisco's policy includes an exception for criminal defendants, but even then, ICE has complained that the city does only the minimum, often only assisting federal officials when they file a formal arrest warrant.

When San Francisco police last arrested Juan Francisco Lopez-Sanchez, the suspect in the July 1 shooting, ICE had asked for a heads-up on if and when he was released, so that it could arrest him on immigration charges and deport him. The city didn't provide that notice, though, and ICE didn't issue an arrest warrant.

Asking cities to keep undocumented immigrants in their jails on ICE's behalf would raise constitutional issues, Pham said. The federal government cannot "commandeer" local governments for its own purposes. But asking for notice is different, she said, and the Justice Department might be able to convince a judge that San Francisco's noncooperation policies go too far.

"I think there would be some possibility of enforcing those two federal provisions," she said—if the federal government wanted to sue noncooperating cities.

Melissa Kearney, a staff attorney with the National Immigration Law Center, said she's not particularly worried about the Justice Department trying to crack down on "sanctuary cities," at least while President Obama is still in office.

Even if a Republican president wanted to change course in 2017, the options for a unilateral Justice Department crackdown might be limited.

"There might be one or two provisions that could violate the federal statute, but the policy—there's a lot to it," Pham said.

According to a 2007 report by the Justice Department's inspector general, San Francisco was the only "sanctuary city" to identify itself as having a policy on the books that prohibited communication with federal immigration officials. Pham said that provision might conflict with federal law, but that the overall noncooperation measure would probably be safe.

"I think they'd have a shot "¦ but only against the one part," she said.

This article is from the archive of our partner National Journal.

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