SAN FRANCISCO — Opponents of a voter-approved measure to speed up executions in California asked the state Supreme Court on Friday to reconsider its ruling upholding the law.

The high court’s decision unconstitutionally delegated power to the judicial branch and failed to consider whether the measure could survive after the justices invalidated “critical features” of the law, attorneys Christina Von der Ahe Rayburn and Lillian Mao said in their court filing.

Last month’s highly anticipated ruling concerned Proposition 66, a push to “mend not end” capital punishment in California.

Condemned inmates in California currently languish for decades and are more likely to die of natural causes than from lethal injection. There are nearly 750 inmates on death row, and only 13 have been executed since 1978 — the last in 2006.

The state Supreme Court upheld requirements in Proposition 66 limiting successive appeals and filing extensions. But it rejected arguments that a provision setting a five-year limit on appeals was mandatory, raising doubts that the law will succeed in accelerating death sentences.

An attorney for supporters of the measure did not immediately return an email seeking comment.

Rayburn and Mao said the court should determine whether voters would have still passed Proposition 66 without the five-year deadline and other deadlines in the measure.

Without the deadlines, the judicial branch had no guidance from the legislative branch about how to implement the measure and would be overstepping its authority if it moved forward with crafting rules for Proposition 66, they also said.