Gov. Gavin Newsom has signed a bill requiring a countywide vote before a local water district can “detach,” though it’s too late to prevent local votes in Fallbrook and Rainbow.

The two rural districts have sought to leave the San Diego County Water Authority for a cheaper, if potentially less reliable water supply from Riverside County.

Assembly Bill 399, introduced by Assemblymember Tasha Boerner of Encinitas and sponsored by the city of San Diego, expands voting requirements should agencies seek to withdraw from any county water authority.

The new law is effective Jan. 1, but the votes in Fallbrook and Rainbow are scheduled for Nov. 7.