Section 203 of the comprehensive Bipartisan Campaign Finance Reform Act of 2002, widely known as the McCain-Feingold law, bans the broadcast of "electioneering communication" by corporations, trade groups, unions and some issue advocacy groups, if the material would air close to election dates and identify candidates by name or image.
The law also requires an on-screen notice of the groups financing such ads, as well as public disclosure of all who donated to the sponsoring organizations.
The landmark McCain-Feingold law took effect the day after the November 2002 elections.
Among its many provisions are a ban on "soft money," the unlimited and unregulated contributions to national political parties; a ban, in the 60 days before an election, on advocacy ads, those criticizing or supporting a candidate's stand on an issue; contribution limits; and donor disclosure requirements.
Much of McCain-Feingold remains unaffected by the high court's latest ruling, including the current ban on large, unregulated donations to political parties and the candidates themselves by corporations. The case also does not affect political action committees, separate groups created by corporations, unions and others that can contribute directly to federal candidates.
PAC money has a $5,000-per-candidate limit, and must be funded through voluntary contributions from employees, members or individuals, not by direct corporate or union treasuries.
The ruling could have far-reaching effects beyond the federal arena. Twenty-two states have similar bans on corporate spending in state and local elections. Restrictions on money in gubernatorial, legislative and even judicial races could soon be a thing of the past.
"Campaign 2010 was already bulked up with the potential of campaign ad spending," said Evan Tracey, president of Campaign Media Analysis Group and CNN's consultant on political television advertising. "Now it's on steroids."