It's not as good as it sounds, as you'll see below. From [1]:

(Yesterday, California governor Jerry Brown) vetoed AB1081 (from Tom Ammiano), which could have protected illegal immigrants from deportation if they committed minor infractions. The bill has been dubbed "anti-Arizona" legislation, a reference to that state's immigrant identification law.

The so-called Trust Act would have let California opt out of some parts of a federal program that requires local law enforcement officers to check the fingerprints of people they arrest against a federal immigration database and hold those who are in the country illegally.

It would have barred local law enforcement officers from detaining suspects for possible deportation unless they are charged with serious or violent felonies.

Here's Brown's statement from his veto of the bill [2]:

Undocumented immigrants play a major role in California's economy, with many performing low-wage jobs that others don't want. Comprehensive immigration reform - including a path to citizenship - would provide tremendous economic benefits and is long overdue. Until we have immigration reform, federal agents shouldn't try to coerce local law enforcement officers into detaining people who've been picked up for minor offenses and pose no reasonable threat to their community.

But I am unable to sign this bill as written. Under the bill, local officers would be prohibited from complying with an immigration detainer unless the person arrested was charged with, or has been previously convicted of, a serious or violent felony. Unfortunately, the list of offenses codified in the bill is fatally flawed because it omits many serious crimes. For example, the bill would bar local cooperation even when the person arrested has been convicted of certain crimes involving child abuse, drug trafficking, selling weapons, using children to sell drugs, or gangs. I believe it's unwise to interfere with a sheriff's discretion to comply with a detainer issued for people with these kinds of troubling criminal records.

The significant flaws in this bill can be fixed, and I will work with the Legislature to see that the bill is corrected forthwith.

That shows you how bad Ammiano's bill was, so bad that even Jerry Brown wouldn't sign it. Expect Ammiano and others to correct those downsides and give Brown a bill he can sign.

If you want to do something about this, help promote the plan on the Question Authority page and find others to help use that plan to discredit Brown and Ammiano on immigration.

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[1] peekURL.com/znMq9az
[2] gov.ca.gov/docs/AB_1081_Veto_Message.pdf