The highly unusual announcement by Ms. Harris — by all appearances, California law gives no discretion to the attorney general in handling these kind of initiatives — comes as gay groups and others have called on her to block the measure. Ms. Harris, who was just elected to a second term, announced earlier this year that she would run for the Senate in 2016.

In her statement, Ms. Harris signaled her absence of legal options as she threw the ball to the courts. “If the court does not grant this relief,” she said, “my office will be forced to issue a title and summary for a proposal that seeks to legalize discrimination and vigilantism.”

Even if she is forced to proceed, Mr. McLaughlin — who did not return a telephone call seeking comment Wednesday — has a tough road ahead. He would have to gather the signatures of 365,880 registered voters in a maximum of 180 days, and it seems highly unlikely that if he succeeded at that, voters in the state would approve a measure like this.

Floyd F. Feeney, a professor of law at the University of California, Davis, said that it was highly unlikely that a court would intervene.

“This is a ministerial duty as opposed to discretionary,” he said of the attorney general’s role in these kind of matters. “Your duty is to do what the statute says to do.”