Counties that limit cooperation with ICE see certain deportations drop by a third, but there’s no measurable effect on crime.

Though much of immigration policy is determined at the federal level, local governments assert themselves where they can, often acting as counterweights: Some enact harsher policies when an administration adopts a more inclusive approach, and others become more welcoming when federal enforcement ramps up.

“Sanctuary” policies, which began under the Obama administration, became a flashpoint after President Trump took office. But for all the high-pitched political energy fueling this debate, it isn’t clear what real-world effects the policies are having, and neither side has had much evidence to support its arguments.

David Hausman, an IPL postdoctoral affiliate, is the author of a new study addressing the central question in the sanctuary debate: whether crime increases when local law enforcement limits its cooperation with Immigration and Customs Enforcement (ICE). Hausman’s findings, published this week in Proceedings of the National Academy of Sciences, challenge both advocates and critics.

On the one hand, these policies do affect ICE: Certain kinds of deportations dropped significantly in sanctuary counties. On the other hand, critics are wrong to say that sanctuary policies threaten public safety. Crime rates stayed the same, people convicted of violent crimes were deported in about the same numbers, and police made arrests for crimes at the same rate as before. These policies, Hausman found, mostly spare the people with no convictions.

“I hope that this study brings some facts to a debate that has too often relied on assertions,” Hausman said.

Delving into the Data

“Sanctuary” can mean many things policy-wise, but Hausman’s study focuses on the most important element: prohibiting local law enforcement from complying when ICE asks them to hold immigrants past their release date. When police officers make an arrest, they send the person’s fingerprints to the FBI, which in turn shares them with ICE. If ICE identifies the person as an immigrant eligible for deportation, it issues a detainer request—a request for the jail to imprison someone for 48 hours beyond when he or she would otherwise be released, in order to make it easier for ICE to arrest the person.

Hausman looked at 369,388 deportations between November 2008 and December 2015 that began when a noncitizen was arrested by local law enforcement. At the time when many sanctuary policies were taking effect (2014–15), this kind of deportation made up 55 percent of all the deportations ICE initiated from the interior of the country.

He focused on 296 large counties, which accounted for more than 80 percent of all deportations that began with a local arrest. Of those 296 counties, 140 adopted sanctuary policies (or were affected by a state sanctuary policy) between 2010 and 2015.

Hausman then compared sanctuary and non-sanctuary counties before and after the policies were adopted. While the two groups looked roughly the same before the polices were introduced, they diverged just a few months afterward:

  • Those with sanctuary policies saw deportations after local arrests fall by a third.
  • Among noncitizens without criminal convictions, sanctuary policies reduced deportations by half.
  • Among noncitizens convicted of violent crimes, sanctuary policies had no measurable effect.
  • Sanctuary policies prevented about 22,300 deportations nationwide between 2013 and 2015, including about 3,300 deportations of immigrants who had never been convicted of any crime.

In a way, it’s not surprising that sanctuary policies did not protect people with convictions for violent crimes. Many sanctuary policies make exceptions for them, allowing local police to comply with ICE detainer requests for noncitizens with these convictions. Moreover, people convicted of violent crimes are more likely to serve sentences in state prisons, where ICE can easily locate them before their release.

To measure the effect of sanctuary on crime, Hausman looked at 224 large counties that consistently reported crime data each month. Sanctuary policies appeared neither to increase crime rates nor help police solve crimes.

Taken together, these findings show that, even as sanctuary policies reduce deportations, they do not harm public safety. They also show that local communities can shape immigration policy. Sanctuary policies tend to be discussed in terms of politics, but they also have significant real-world effects—not least for the people who remain in the country today because these policies were in place.