A California father whose son was murdered execution-style in 2008 by an illegal immigrant gangster has launched a campaign to persuade Gov. Jerry Brown to veto a bill that would have police release illegal immigrants into the streets even when the feds want them detained.

The controversial bill, which passed the legislature in August, would compel local law enforcement in most cases to ignore requests by Immigration and Customs Enforcement to hold illegal immigrants if they could otherwise be released.

Advocates say it's a way for police to build "trust" with local communities -- the name of the bill is the TRUST Act. But opponents warn the policy could have dangerous consequences.

The bill "will have real and potentially devastating consequences for people across our state," Jamiel Shaw Sr., whose 17-year-old son was killed, said in a statement.

Shaw separately put out a web video appealing to Brown to reject the bill.

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"Would you want that to happen to your son? ... How many have to die by people being let out into the streets from the county jail that should be deported," he said in the video. "No one should have to go through losing a child."

Click for the original story on Shaw's case.

Shaw's son Jamiel Shaw Jr., a high school football player, was killed in 2008 by a member of the 18th Street Gang hours after he had been released from a local jail. Pedro Espinoza was found guilty of the murder, in which he shot Shaw twice after mistaking him for a rival gang member. A jury recommended the death penalty for Espinoza earlier this year.

Bob Dane, a spokesman at the Federation for American Immigration Reform, said California would open the door to a rampant public safety threat -- as well as additional financial burden on the state -- if the governor lets the bill become law. He noted Brown could opt to take no action on the bill, allowing it to become law by default.

"It's the perfect storm for complete lawlessness," he told FoxNews.com, saying the state would be rolling out "the welcome mat" for illegal immigrants and become even more of a magnet.

"This is not the work of responsible custodians of the public trust," he said.

The bill would compel law enforcement in California to release illegal immigrants once they become eligible -- even if ICE wants them held -- unless the individual has been convicted of a "serious or violent felony."

Supporters cited the financial burden on local communities that hold these detainees for ICE and the potential erosion of trust with police.

In a Sept. 13 letter to Brown signed by House Democratic Leader Nancy Pelosi and other Democratic members of the California congressional delegation, supporters urged the governor to sign the bill. They cited accounts that a federal program called Secure Communities "currently erodes trust between local communities and law enforcement."

"They report that the initiative already has reduced the willingness of immigrant and non-immigrant crime victims and witnesses to cooperate with law enforcement and has consequently diminished public safety," they wrote. The suggestion is that illegal immigrants would be reluctant to report crimes out of concern ICE would come after them.

Secure Communities is a program that allows federal immigration agents to work with local officials to determine who in local jails might be deportable.

But Shaw argues that police in California are not interested in checking the immigration status of people who report or witness crimes.

Further, he argues that in California in particular, illegal immigrants are not fearful of law enforcement.

Federal immigration officials have defended the Secure Communities program, which they say has helped the agency remove nearly 150,000 convicted criminals to date -- including murderers and rapists.

ICE Director John Morton wrote in an Aug. 23 letter to FAIR that communities that ignore ICE requests to hold detainees "are undermining public safety in their communities by exposing their local communities to risks from suspected and convicted sex offenders, weapons violators, drunk drivers and other violent criminals."

"These are not hypothetical risks," he wrote. The letter was in reference to a separate initiative in Illinois.

ICE spokeswoman Gillian Christensen told FoxNews.com on Wednesday that the agency implements "clear priorities" to focus on convicted criminals. She stressed the importance of local cooperation, without commenting specifically on the California proposal.

"The federal government alone sets these priorities and places detainers on individuals arrested on criminal charges to ensure that dangerous criminal aliens and other priority individuals are not released from prisons/jails and into our communities," she said. "The Administration remains committed to immigration reform and to enforcing current law in a smart and effective manner across the country."