The D.C. Court of Appeals overturned an earlier District Court ruling Tuesday that required outside groups to disclose some of their donors.

On March 30, the District Court found in favor of Rep. Chris Van Hollen (D-Md.), who sued the FEC over its regulation that donations of $1,000 or more to corporations, labor organizations and nonprofits need only be disclosed when designated for “electioneering communications." An electioneering communication covers any targeted broadcast, cable or satellite ad, made within 30 days of a primary or 60 days of a general election that directly identifies a candidate for federal office.

The previous ruling mandated that outside groups running so-called issue ads disclose their donors, but groups moved to avoid that requirement by shifting the nature of their ads. The U.S. Chamber of Commerce, for example, began running independent expenditure ads that expressly advocated for the election or defeat of a candidate.

Both the Hispanic Leadership Fund and Center for Individual Freedom appealed the case—the higher court finding itself unable to shed light on the question without the FEC’s involvement in the case. The FEC is expected to either conduct a new rulemaking or leave the matter up to the district court judge.

In a statement released after Tuesday's decision, Van Hollen said he hopes the FEC will require disclosure or that the court will strike down their regulation as “arbitrary and capricious."

“Today the D.C. Court of Appeals struck a blow against transparency in the funding of political campaigns and reinstated the flawed regulation that rendered the disclosure requirements meaningless—made clear by the fact that millions of dollars of special interest money has flooded the airwaves with ads from anonymous sources,” Van Hollen said in a statement. “The Court of Appeals’ decision today will keep the American people, for the time being, in the dark about who is attempting to influence their vote with secret money.”