The controversy over the federal immigration enforcement program known as Secure Communities has been brewing since not long after it was first implemented 2008, during the waning days of the Bush administration. But after a heated back-and-forth between state, local and federal officials over the program as some jurisdictions attempted to withdraw – only to be told they couldn’t – the controversy came to a head this year.

First, in a nutshell, how Secure Communities works: When state or local authorities book someone into a local jail, the person’s fingerprints are electronically submitted to the FBI. These fingerprints are then sent to the Department of Homeland Security, and U.S. Immigration and Customs Enforcement agents check them against an immigration records database to determine if the person is deportable (legal residents are also subject to deportation if they have committed certain offenses). The person is then held for deportation by ICE.

Unlike with a similar federal-local partnership known as 287(g), the screening is done pre-conviction, meaning that some people who turn out to be otherwise innocent have landed in the deportation net; some cases have involved domestic violence victims. This has been a sticking point for critics of the program, who say it goes against the Obama administration’s stated goal of focusing on criminals for deportation. Criticism has also come from some law enforcement agencies, state and city officials who complain that because of its nature, the program alienates immigrant communities by undermining trust in police, making policing them more difficult.

Which brings us to this year’s explosive controversy: Several jurisdictions around the country, including the city of San Francisco, began attempting to opt out of the program last year. Many local and state officials had believed that as with 287(g), Secure Communities was optional, as evidenced by a series of internal emails released last spring. After all, federal officials had signed contracts known as Memorandums of Agreement, or MOAs, with state and local officials around the country allowing Secure Communities to be implemented.

Read the full story at Southern California Public Radio