Others believe voters will wind up with less information before they cast their ballot in November. David Keating, the president of the Institute for Free Speech, which supports the deregulation of campaign finance, said the decision will almost certainly throw a wet blanket on independent expenditures from now to the November 6 midterm elections.

“We think that’s a real prospect—that a number of groups are going to choose silence rather than speech—and there are good reasons why they would do that,” Keating said. “Certainly not all but most of these groups may come to the conclusion this is too risky: ‘Our donors gave us money under the assumption they would remain confidential, and we don’t want to do things that would make them not give us money anymore.’”

Weintraub said it wouldn’t be surprising to see some groups “come up with clever ways of getting around the rules.” She expects FEC commissioners to come together soon in an effort to clarify which donors need to be disclosed. But that could be difficult, given that the FEC’s four remaining commissioners are often at ideological odds with one another.

Today’s decision is six years in the making. It stems from a complaint filed by Citizens for Responsibility and Ethics in Washington (CREW), a campaign-finance-reform group, with the FEC against Crossroads GPS, a conservative nonprofit organization that has spent tens of millions of dollars to boost Republican political candidates. CREW alleged that Crossroads GPS was violating federal law by keeping its donors secret.

The FEC in 2015 deadlocked 3–3 on whether to investigate Crossroads GPS. In 2016, CREW then sued the FEC. Last month, U.S. District Court Chief Judge Beryl A. Howell ruled for CREW. She gave the FEC 45 days to issue a new regulation that would require donor disclosure in accordance with the law.

Crossroads GPS sought an emergency stay from the D.C. Circuit, which declined to grant it. Supreme Court Chief Justice John Roberts stayed the lower court’s decision on Saturday, but the stay was brief: The full Supreme Court vacated Roberts’s stay, allowing Howell’s ruling to stand.

The high court’s action is tempered by two considerations. The decision appears to leave a loophole: Some super PACs, which must disclose their donors publicly, accept money from nonprofit groups. Conceivably, a super PAC could take money from a nonprofit group that doesn’t itself advocate for or against political candidates—meaning the super PAC could continue hiding the flesh-and-blood source of the cash funding its efforts, several election lawyers told the Center for Public Integrity. Also, the original case that prompted today’s action, Citizens for Responsibility and Ethics in Washington v. Federal Election Commission and Crossroads GPS, remains under appeal, meaning today’s decision could be temporary—or not.