Seattle’s election commission says Facebook broke a city law that requires it to disclose who paid for campaign ads. Reuters reports that the Seattle Ethics and Elections Commission’s executive director, Wayne Barnett, said Facebook must reveal advertising spending information for last year’s city elections or potentially face fines of up to $5,000 per ad purchase.

Facebook, Twitter and Google have been under scrutiny since being called to testify as part of a Senate investigation into how social media might have been used by Russians to interfere with the presidential election. Last fall, Facebook promised more transparency into political ads on its platform, including tools that allow users to see who paid for them, after admitting that more than 3,000 ads related to the 2016 U.S. presidential election were bought by buyers linked to Russia.

Facebook vice president Will Castleberry told Reuters that the company “is a strong supporter of transparency in political advertising. In response to a request from the Seattle Ethics and Elections Commission we were able to provide relevant information.” Barnett insists, however, that Facebook hasn’t “come close to meeting their public obligation” despite meeting with city officials and giving them partial spending data.

Even though Facebook has vowed to give more details about campaign ad spending, Seattle may be the first municipality that forces it to do so. At the heart of the issue is the fact that most local and federal laws governing how radio, television and cable companies approach political ads—for example, by requiring them to ensure airtime is allocated equally to candidates and requiring political committees to disclose ad spending—were written before the rise of social media. As a result, there is ample confusion over how laws apply to online platforms like Facebook.

TechCrunch has contacted the Seattle Ethics and Elections Commission and Facebook for comment.

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