California lawmakers consider new rules for political ads.

SACRAMENTO, Calif. — Facebook users in California may have noticed ads in recent months showing a woman with duct tape over her mouth and text that warns: “Legislators are leaving sexual assault survivors from public universities out to dry.”

The ads urge readers to sign a petition seeking to add public universities to legislation that would give students at private universities more time to sue their schools over sexual assaults.

Neither the ads nor the website where they lead offer any clue about who is paying for them. Unlike most election season ads about candidates or ballot measures, they don’t have to.

Now, California legislators are considering a proposal by Assemblyman Kevin Mullin that would require groups buying such “issue advocacy ads” about legislation to identify themselves and major funders in the same sort of disclaimers required in election campaign commercials.

“This is about well-funded, sophisticated special interests,” said Mullin, a San Mateo Democrat.

Proponents say the measure would be the first in the U.S. to address what they see as a burgeoning issue in the world of influence peddling as interest groups seize on the anonymity afforded by the internet and social media advertising.

“I’ve never seen so many issue ads,” said Trent Lange, president and executive director of California Clean Money Campaign, which is sponsoring Mullin’s bill.

Critics argue the proposed law would discourage grassroots activism, particularly around hot-button issues.

Current law requires groups lobbying the California Legislature to disclose expenses such as advertising in routine quarterly filings with the secretary of state.

But an ad campaign may be over at that point, and groups do not necessarily have to specify which ads they funded, noted Kati Phillips, spokeswoman for the campaign finance reform group Common Cause California, which supports Mullin’s bill.

Chasing down who exactly is behind an advertising campaign to influence legislation at California’s Capitol can be a journey through corporation filings, political spending disclosures and anonymous social media pages — all sometimes leading to a dead end.

Kevin Mullin