Gov. Jerry Brown blocked parole for a former leader of the notorious Mexican Mafia prison gang who has turned on his former comrades and now aids law enforcement.

Brown announced Friday that he was blocking the release of 52-year-old Rene "Boxer" Enriquez.

"Because he is a high-profile drop out targeted by the Mexican Mafia, Mr. Enriquez' parole poses a serious security risk to him, his family, his parole agents, and the community in which he is placed," Brown wrote.

Enriquez has been in prison since 1993 serving a sentence of 20 years-to life in prison for two murders, multiple assaults and conspiracy to traffic in controlled substances.

He drew attention last month when elite Los Angeles Police Department officers cleared a downtown Los Angeles building so Enriquez could speak to a gathering of police chiefs and business leaders about the growth and operations of a prison gang that has evolved into a transnational criminal enterprise.

The Los Angeles District Attorney's Office opposed his parole request, although he had letters of support from the FBI; several deputy district attorneys; a deputy state attorney general; three assistant U.S. Attorneys; and several officers from local forces and the California Department of Corrections and Rehabilitation, according to the transcript.

He published a tell-all book, "The Black Hand," using a nickname for the gang also known by its Spanish language initial, La Eme.

His brazenness was demonstrated in 1991, when he and another man assaulted Mexican Mafia leader Salvador "Mon" Buenrostro at a lawyers' interview room in the Los Angeles County Jail. They stabbed him 26 times but Buenrostro survived.

Enriquez testified that he was dragged into a gang at the age of 12 or 13, when members of a Los Angeles street gang beat him behind a gas station as an initiation. He went to juvenile hall after he and two other partygoers raped an intoxicated woman. He joined the Mexican Mafia during his first stint in prison.

That made him "one of the top apex predators" in a violent universe, Enriquez said at his parole hearing in September. He said he eventually rose to become "part of the orchestrating leadership structure" that organized drug trafficking and directed murders and other street crimes from behind prison walls.

Once he began cooperating with authorities in 2005, the government went to extraordinary lengths to protect him, at one point booking him into custody under a false name for possession of a swordfish without a license, which Enriquez said was a bogus or "ghost" charge to protect him.

He testified that he was being paid a stipend of $200 a week for work that includes giving lectures to California law enforcement officials and teaching an online course on major prison gangs.