The California Supreme Court had ruled on February 17, 1972, that capital punishment was contrary to the state constitution.
It was submitted to a referendum by means of the initiative process, and approved by voters on November 7 with 67.5% of the vote.
Proposition 17 amended the state constitution by adding Article 1, Section 27, which reads: All statutes of this state in effect on February 17, 1972, requiring, authorizing, imposing, or relating to the death penalty are in full force and effect, subject to legislative amendment or repeal by statute, initiative, or referendum.
Justice Stanley Mosk filed a concurring opinion in which he reluctantly agreed with the judgment of the court, but also expressed his dismay at the response of the electorate to Anderson: The people of California responded quickly and emphatically, both directly and through their elected representatives, to callously declare that whatever the trends elsewhere in the nation and the world, society in our state does not deem the retributive extinction of a human life to be either cruel or unusual.
This was due to the U.S. Supreme Court decision in the same year in Furman v. Georgia (which temporarily halted capital punishment in the United States) and to extensive litigation that occurred thereafter.