Local police should not be put into the immigration enforcement business.

Arizona recently passed a law requiring police to determine the immigration status of any person when officers have “reasonable suspicion” that the person is “unlawfully present” in the country.

But police chiefs and officers around the country agree that this is a bad idea.

There is nothing wrong at all with immigration enforcement; every nation has a right to secure its borders.

This task requires a comprehensive effort staffed by federal agents, however. Using local police officers for immigration purposes undermines their mission: working with their communities to ensure safety.

And it runs counter to the theory and practice of community policing.

Community policing has spread across the United States because its success is based on common sense. If we want safe streets, police and the people they serve must work together as partners. The police cannot create public safety alone; they must have the cooperation, support and information that only the community can provide.

This kind of a partnership requires one ingredient above all: trust. The community must trust that the police have its interests at heart. If that trust disappears, fear will govern instead. And when residents fear that they or their family members risk deportation in any contact with police, they will avoid that contact, whether they witness crimes or are victimized by them.

In the bargain, criminals remain free to prey on others.

Police officers understand this. That explains why the Major Cities Chiefs Association, a professional association of the chiefs of police in the largest cities in the United States, has taken a strong position against involving local police agencies in immigration enforcement. Having local police participate in these efforts “undermines the trust and cooperation with immigrant communities which are essential elements of community-oriented policing,” the police group has said.

Involving police officers in immigration enforcement actually hurts public safety. Some of the best evidence of this comes from Arizona itself. The Goldwater Institute, a conservative think tank, studied the data describing what happened when Maricopa County Sheriff Joe Arpaio moved many of his deputies into immigration enforcement tasks instead of policing Phoenix and the surrounding area. The bottom line: Everyone’s safety suffered. The sheriff’s department “has diverted resources away from basic law-enforcement functions to highly publicized immigration sweeps, which are ineffective in policing illegal immigration and in reducing crime generally,” the report said, adding that violent crime went up after the focus shifted to immigration enforcement instead of public safety.

We should listen carefully to our law enforcement experts when they caution us against giving local police an impossible task that will destroy their ability to accomplish their core mission.

Being a police officer is hard enough already. We don’t need to make it any harder.

David A. Harris is professor of law at the University of Pittsburgh. He studies police behavior and search and seizure law, and has written and testified extensively about local police agencies and immigration enforcement. He can be reached at pmproj [at] progressive [dot] org.