Today’s ruling in the campaign-finance case focused on the Supreme Court’s decision in 2003, when there was a different lineup of justices, upholding a key section of the McCain-Feingold law. That section bars companies and unions from paying for ads even mentioning the name of a candidate for federal office in the 60 days before a general election or the 30 days before a primary.

The 2004 ads in question mentioned Senators Russell D. Feingold and Herb Kohl, both Wisconsin Democrats, and urged viewers to contact them and urge them to oppose their Democratic colleagues’ opposition to some of President Bush’s judicial nominees. The ads directed viewers to a Web site critical of Mr. Feingold, who was up for re-election.

Mr. Feingold and Senator John McCain, Republican of Arizona, were the main sponsors of the campaign finance law. Its supporters see it as a valiant attempt to regulate the spigots that pour oceans of corrupting money into political campaigns. Its detractors see it as interference with free speech, and as unrealistic in view of the huge sums of money needed to run a political campaign.

The Wisconsin Right to Life organization sued the Federal Election Commission, seeking a judgment declaring that the pertinent McCain-Feingold section was unconstitutional. A special three-judge federal court panel ruled in favor of the anti-abortion group, finding that the ads’ text and images did not show that they were “intended to influence the voters’ decisions” but were “genuine issue ads” that the government could not keep off the air.

Today, the Supreme Court majority concluded that the special judicial panel was right in holding that the ads should have been allowed. “Because WRTL’s ads may reasonably be interpreted as something other than an appeal to vote for or against a specific candidate, they are not the functional equivalent of express advocacy,” the majority said, using the term for ads that urge a candidate’s election or defeat.