The decision was a reminder of the ways in which the justices appointed by President Bush are moving the court. While Chief Justice Roberts’s predecessor, Chief Justice William H. Rehnquist, was a dissenter when the court upheld the law four years ago, Justice Sandra Day O’Connor was in the 5-to-4 majority. Her successor, Justice Samuel A. Alito Jr., voted with Chief Justice Roberts on Monday, and in fact was the only justice to join his opinion fully.  Two other closely divided rulings announced on Monday also showed the influence of the new justices. The court limited student speech and ruled that taxpayers do not have standing to challenge the administration’s program of support for social service programs offered by religious institutions.  Coming as the 2008 presidential race takes off, the campaign finance decision has the effect of jettisoning a major part of the McCain-Feingold law, which Congress passed in 2002 to curb the flow of unregulated “soft money” into federal election campaigns.  While the decision did not deal directly with the soft-money ban, which is in a separate section of the law, election experts said the effect would be to undercut the soft-money section as well by permitting a largely unlimited flow of money from corporate treasuries to pay for the all-important broadcast advertisements in the weeks before primary and general elections. Groups seeking to influence the outcome of the election could easily sidestep the prohibition on explicit appeals for or against candidates, supporters of the law said.  It is not clear which candidate or party is more likely to benefit from the ruling in 2008. But Senator John McCain, the Arizona Republican seeking his party’s presidential nomination, may suffer the most in the short term. His sponsorship of the law, formally called the Bipartisan Campaign Reform Act, is unpopular with conservatives and Republican primary voters, and the Supreme Court’s decision is a reminder of his role.  Although the court’s five most conservative justices voted in the majority and the four more liberal justices were the dissenters, the outcome was not easy to categorize simply along ideological lines. Both sides of the campaign finance debate have always attracted unusual coalitions. Chief Justice Roberts pointed out in his opinion that among the groups supporting the challenge to the law, which was brought by the Wisconsin Right to Life, were the American Civil Liberties Union and the A.F.L.-C.I.O., as well as the United States Chamber of Commerce and the National Rifle Association.  The dissenters, Justices David H. Souter, John Paul Stevens, Ruth Bader Ginsburg and Stephen G. Breyer, said the decision stood the court’s earlier interpretation of the statute “on its head” and would invite the “easy circumvention” of the sponsors’ purpose.  The dissenters’ argument that the court had effectively overruled its 2003 decision in McConnell v. Federal Election Commission, presented in an opinion by Justice Souter, found agreement among election law experts.  “Corporations received the victory that they did not achieve in 2003,” said Edward B. Foley, a professor at the Moritz College of Law at Ohio State University.  It may be only a matter of time before the court reconsiders its 2003 decision upholding the constitutionality of the entire law, or at least expands its Monday decision to strike down any restriction on advertising. Three of the five justices in the majority, Antonin Scalia, Anthony M. Kennedy and Clarence Thomas, declined to sign the chief justice’s opinion because it did not take that step.  In fact, Justice Scalia, in a footnote to his separate opinion, agreed with the dissenters that the court has in effect already reversed the 2003 decision when it came to the advertising restriction. The decision changed the law so substantially that it “effectively overrules” the 2003 decision “without saying so,” Justice Scalia said. And demonstrating that he does not consider the new chief justice immune from the insults for which his opinions are famous, he added: “This faux judicial restraint is judicial obfuscation.”  Justice Alito indicated in a separate opinion that he, too, would be open to reconsidering the earlier decision, as “we will presumably be asked in a future case” to do.  Legal experts and political advocates said the ruling, Federal Election Commission v. Wisconsin Right to Life Inc., No. 06-969, represented a swing back from a tighter approach toward regulating political contributions that peaked with passage of the 2002 law.  Congress enacted the law in part in reaction to a flood of special interest money into both parties. Throughout the 1990s, both parties had aggressively courted contributions to their allied party committees from corporations, unions and wealthy individuals for the express purpose of winning elections.  These donations, known as soft money, thus circumvented the limits on campaign contributions under older campaign laws. The McCain-Feingold law sought to end the use of soft money in part by barring corporations and unions from contributing to parties or political action committees.  The new decision brings back soft money, said Kenneth A. Gross, a Washington lawyer who represents corporations in election law matters. “The significance of it is, you can use soft money to do these ads,” he said. “This is a clear shot over the bow by this court that there is going to be less regulation of money in politics. The fulcrum has now shifted.”  It remains to be seen how the Federal Election Commission applies the new ruling. The decision held that Wisconsin Right to Life had a constitutional right to run three television commercials in 2004 that criticized Senator Russ Feingold, Democrat of Wisconsin, for helping to block Mr. Bush’s judicial nominees. Contact the senator, the commercials said.  Wisconsin Right to Life conceded that the advertisements were prohibited by the statute because they named Mr. Feingold, who was seeking re-election; were intended to reach Wisconsin voters; and were to run during the law’s 30-day blackout period before the primary. So the question was whether they were nonetheless permitted by the First Amendment, as a special three-judge Federal District Court here held that they were. The decision on Monday upheld that ruling.  In its decision in 2003, the Supreme Court ruled that the advertising restriction was not unconstitutional “on its face.” Although many assumed that the ruling ended the matter, James Bopp Jr., Wisconsin Right to Life’s counsel, pressed for the right to challenge the restriction “as applied” to his group and others like it, which he said were engaged in constitutionally protected issue advocacy, albeit with corporate contributions.  In its last term, the Supreme Court gave the go-ahead for “as applied” challenges, a signal that the court might soon be taking a different view of the law.  The law’s supporters, including Fred Wertheimer, a longtime advocate of tighter campaign laws, asserted on Monday that a remaining part of the law, prohibiting federal officials from soliciting soft money, was still extremely important.  Mr. McCain agreed. While calling the decision “regrettable,” he pointed out that the solicitation ban was unaffected. “Fortunately, that central reform still stands as the law,” he said.  A version of this article appears in print on , on Page A1 of the New York edition with the headline: Justices Loosen Ad Restrictions In Campaign Law. Order Reprints| Today's Paper|Subscribe
The Supreme Court’s 5-4 ruling opened a significant loophole in the 2002 McCain-Feingold law and may affect the strategy of the 2008 campaigns.