California Attorney General Kamala Harris has told law enforcement officials in the nation’s largest state that the Secure Communities program of the Department of Homeland Security is optional.

It was Harris’ first public assessment of Secure Communities. Under the program launched in 2008, all arrestees’ fingerprints are sent to immigration officials, who may ask police and sheriff’s departments to hold suspects for up to 48 hours after their scheduled release so they can be transferred to federal custody.

Although the intent may have been to improve public safety, Harris said that a review of data from March through June showed that 28% of those targeted for deportation in California as a result were not criminals. Those numbers, she noted, had changed little since U.S. Immigration and Customs Enforcement a year earlier pledged to reform the program to focus on the most serious offenders.

“Secure Communities has not held up to what it aspired to be,” Harris said. The law enforcement bulletin she issued Tuesday stated that “immigration detainer requests are not mandatory, and each agency may make its own decision” about whether to honor them.

This is a very big deal. Immigrant rights activists have criticized the S-COMM program for years, saying that it swept up too many non-criminals in its net. Activists have presented stories about victims of domestic violence getting screened for immigration status, and deported as a result, or individuals coming forward to give tips about serious crimes getting the same treatment. The program broke the bonds in Hispanic communities between citizens and law enforcement, and as a result it was making local law enforcement’s jobs harder. Harris reflected this in her statement on the change, saying, “I want that rape victim to be absolutely secure that if she waves down an officer in a car that she will be protected … and not fear that she’s waving down an immigration officer.”

DHS and Immigrations and Customs Enforcement repeatedly gave assurances that they would only direct resources at criminal undocumenteds, but the statistics speak for themselves. S-COMM and other programs have led to record deportations. And now, Harris, normally a pretty staunch ally of the President, directs California officials to ignore S-COMM. That eliminates its impact in a state with close to 10% of the population and a much higher percentage of undocumented immigrants. Short of actually shutting down S-COMM, this is the biggest possible hit to the program.

Activists still weren’t fully pleased with Harris’ announcement, because it allows for police chiefs and sheriffs to work with S-COMM on a voluntary basis, which could mean different rules depending on various counties or localities in California. I don’t know that Harris could have done much more, but activists say she could have put in place a statewide standard to simply ignore or limit ICE requests. But Jerry Brown vetoed a bill that would have accomplished that earlier this year. The bill’s sponsor, Tom Ammiano, introduced a new version of the Trust Act, and Harris said she would take a look at it.

We’ll have to see how DHS reacts to this.