As a Democrat and former Catholic seminarian, Mr. Brown was caught between two opposing sides of the right-to-die debate, and had given little indication of whether he would sign the bill before it reached his desk in early September.

In the end, I was left to reflect on what I would want in the face of my own death," Mr. Brown said in his signing statement. "I do not know what I would do if I were dying in prolonged and excruciating pain. I am certain, however, that it would be a comfort to be able to consider the options afforded by this bill. And I wouldn't deny that right to others."

Groups like Not Dead Yet and Californians Against Assisted Suicide had joined the Catholic Church in opposing the legislation, arguing that it would place pressure on the ill and disabled to end their lives rather than run up large health insurance bills.

"This is a dark day for California and for the Brown legacy," said Californians Against Assisted Suicide spokesman Tim Rosales in a statement.