The sixth anniversary of Citizens United is predictably leading to more frustration than celebration.

In a letter this week, Reps. John Yarmuth, D-Ky., and Anna Eshoo, D-Calif., led 168 House Democrats to scorn the Federal Communications Commission (FCC), the federal agency charged with oversight of our communications systems, for its failure to enforce rules that require advertisers to adequately disclose the true sponsors of political advertisements.

“In today’s political reality of non-stop campaigning, our system continues to fail the American people by allowing special interests and shadow groups to flood our airwaves with anonymous ads with no disclosure whatsoever,” Yarmuth and Eshoo said in a press release. “We believe the Federal Communications Commission has the responsibility and legal authority to require disclosure of the actual donors behind these ads.”

Referencing Section 317 of the Communications Act of 1934, the House members assert the FCC’s responsibility to require broadcasters to disclose the “true identity” of people, corporations or other entities paying for an ad. We previously explained everything you need to know about political ads — including some reasons why disclosure around them is so poor.

Top Democrats in the House and Senate – including Yarmuth and Eshoo – tried to pass similar legislation last year in the Keeping Our Campaigns Honest (KOCH) Act, named after billionaires David and Charles Koch, whose network of political nonprofits air many of these mysterious ads. The bill — which would have required the FCC to update and enforce its sponsorship identification rules — was defeated in committee.

The letter argues that the acting interpretation of the law is obsolete due to today’s flood of anonymous donors. With the 2016 election set to break records for campaign spending, the hundreds of millions of dollars spent on television advertising create a new web of influence that largely remains in the dark.

“The lack of transparency in politics is harming our democracy, breeding even more mistrust in government, and depressing voter participation,” the members pen in their letter. “The public has a right to know who is trying to influence their vote over the public airwaves and the FCC should honor that right.”

The Sunlight Foundation, the Campaign Legal Center and Common Cause have also urged the FCC to enforce these rules; previously, we’ve pointed out that ads from the super PACs Independence USA (backed by Michael Bloomberg) and NextGen Action Fund (backed by Tom Steyer) ran ads without identifying their sponsor.

“Viewers have more information about what ingredients are in their favorite soft drink, than they do about those trying to influence their vote,” said Meredith McGehee of the Campaign Legal Center.

While there’s more work to do to make information about the people and groups behind political ads available, the FCC is set to vote to expand online political ad disclosure to include cable, radio and satellite providers. Currently only broadcast TV stations are required to publish their political ad files, which contain information about the ads airing, online.