The day before Election Day, a three-judge federal panel returned a debate about campaign finance to the Supreme Court. (Gary Cameron/Reuters)

A three-judge federal panel Monday dismissed a renewed Republican challenge to the “soft-money” ban on unlimited donationstopolitical parties from wealthy individuals, corporations and advocacy groups like unions in a decision that returns the fight over a landmark campaign finance law to the U.S. Supreme Court.

The panel in Washington ruled in a 2015 lawsuit by the Republican Party of Louisiana and two parish GOP affiliates that sought to overturn the last major remaining provision of the Bipartisan Campaign Reform Act of 2002, more commonly known as McCain-Feingold after its chief Senate sponsors.

The law allows for lower court rulings to be appealed directly to the Supreme Court, bypassing intermediate steps, and requires the high court to decide the case.

James Bopp Jr., the lead lawyer for the plaintiffs who sued the Federal Election Commission, said Monday that “we just believe they’re wrong, and we’re certainly appealing to the Supreme Court.”

Once an appeal is filed, Bopp said he would expect a case to reach the high court by February for consideration next year or in 2018.

Bopp has argued that a 2003 Supreme Court decision upholding the party soft-money ban on contributionsto political parties has been overtaken by the high court’s 2010 ruling in Citizens United v. FEC, which ended limits on corporate spending and enabled the growth of super PACs, independent groups funded by massive gifts from big money donors.

The Supreme Court in June 2010 affirmed without comment a ruling by a special three-judge district court panel, also in Washington, that upheld the constitutionality of the soft money-ban in a case brought by the Republican National Committee.

The RNC had argued that the law violates the First Amendment rights of political parties engaged in state elections that have only an incidental effect on federal races. In the RNC challenge, the three-judge panel cited the Supreme Court’s 2003 finding upholding the ban that said there is “no meaningful distinction” between national party committees and the elected officials who control them, and that “large soft-money contributions to national parties are likely to create actual or apparent indebtedness on the part of federal officeholders.”

In the current case, Bopp said even if the ban is constitutionally acceptable on its face, the way it has been applied is not. He argued that before the soft-money ban, state parties could engage in “independent” spending, such as voter-registration activity or advertising without coordinating with any federal candidate or campaign.

By counting such efforts as federal election activities under the soft-money ban, the law leaves political parties at a disadvantage to the super PACs, he said.

The disadvantage persists despite the Supreme Court decision in Citizens United that accepted that independent spending did not pose a risk of “quid pro quo” corruption, Bopp argued.

The courts’ prior rulings were enough to dismiss the Louisiana GOP case, wrote Judge Sri Srinivasan, who ordinarily sits on the U.S. Court of Appeals for the D.C. Circuit but wrote for the panel in Monday’s decision.

“We see no salient distinction between the First Amendment claims rejected in those cases and the challenge presented here,” Srinivasan wrote, with U.S. district judges Christopher R. Cooper and Tanya S. Chutkan.

As in the RNC case, “plaintiffs cannot ‘deny that their proposed activities’ ” would benefit federal candidates, even indirectly, the judges wrote. They added that the high court’s opinion about “independent” expenditures applied to spending, and did not dismiss the risk of corruption from unlimited contributions from donors seeking access to elected officials. Exempting state parties from a ban on unlimited soft-money contributions would simply allow the national parties to resume using state and local affiliates to take in such money, the judges wrote.

An FEC spokeswoman declined to comment on Monday’s ruling.

Public interest groups that support campaign finance laws praised the ruling.

“We are pleased to see they recognized what courts have held for decades, which is that party contribution limits prevent quid-pro-quo corruption and should be upheld,” said Daniel I. Weiner, senior counsel with the Brennan Center for Justice, which with Public Citizen, Democracy 21 and the Campaign Legal Center filed friend-of-the-court briefs supporting the FEC.