Conservative and libertarian groups welcomed the Supreme Court decision, including Steve Simpson with the Institute for Justice. He spoke to reporters in front of the Supreme Court.

"The Supreme Court recognized today that the purpose of the First Amendment is to allow individuals and Americans to speak out as loudly and as robustly as they please," he said. "That applies whether an individual chooses to speak out alone or whether he chooses to associate with others and speak out as a group."

The court's liberal four-member minority opposed the change. In his written dissent, Justice John Paul Stevens said the ruling threatens to undermine the integrity of elected institutions around the nation.

A written statement from President Obama at the White House said the high court's decision opens the way to a stampede of special interest money in American politics.

Among those speaking out in opposition was Democratic Senator Charles Schumer of New York.

"Today's ruling, decided by the slimmest of majorities, guts our system of free and fair elections," he said. "The bottom line is this. The Supreme Court has just predetermined the winners of next November's elections. It won't be Republicans. It won't be Democrats. It will be corporate America."

The high court ruling does not change a ban on direct contributions to candidates from corporations and labor unions that originated back in 1907.