"In this case, voters have decided, for themselves, that they trust the staff and volunteers at their local political Party headquarters, or their church, or a business that they patronize, to securely deliver their completed VBM [vote-by-mail] ballot to the appropriate election official," reads the letter from election attorney Thomas W. Hiltachk.
Addressed to California's Department of Justice and Secretary of State, it adds that "there is no law that requires a third-party recipient of a VBM ballot to fill out the identification envelope or imposes any penalty for the failure to do so."
"Based on the foregoing,it is legal for any organization, or other person, to accept completed VBM ballots from any voter - whether that is at a local Party headquarters, a church, or a union hall, or a voter's doorstep."
Secretary of State Alex Padilla and Attorney General Xavier Becerra had accused the state's GOP of misleading voters about the nature of the boxes.
"Misleading voters is wrong, regardless of who is doing it," Padilla said in a press release. "Political parties and campaigns can engage in get out the vote efforts, but they cannot violate state law. The unofficial, unauthorized drop boxes in question violate state law and jeopardize the security of voters' ballots ... These unauthorized drop boxes are a disservice to elections administrators and a disservice to voters who deserve to cast their ballots with clarity and confidence."
Their letter came in the wake of reports in recent weeks that unofficial ballot drop boxes have been popping up in Fresno, Orange, and Los Angeles counties. They've reportedly been spotted at local political party offices, candidate headquarters, and churches.
Once a voter fills out a ballot, anyone can return it. Most people mail them in prepaid envelopes provided by their county election offices. But others place them in official ballot drop boxes spread throughout the county.
Wednesday, Hiltachk blamed "perhaps an overzealous volunteer" for mislabeling some drop boxes as "official," the Associated Press reported. He said none of the boxes now carry those labels.
Fox News' Bradford Betz, Danielle Wallace, and The Associated Press contributed to this report.