The U.S. Supreme Court ruled on Thursday that corporations can spend freely to support or oppose for presidential and congressional elections.

That decision will transform the political landscape and the rules on how money can be spent in this year's congressional election and the 2012 presidential contest.

By a 5-4 vote, the court overturned a 20-year-old ruling that said corporations can be prohibited from using money from their general treasuries to pay for campaign ads.

 It was a defeat for the Obama administration and supporters of campaign finance laws who said that ending the limits would unleash a flood of corporate money into the political system.

President Barack Obama said on Thursday his administration was in the process of reviewing the decision.

We're studying it, Obama said, responding to a shouted question about Thursday's ruling from a reporter.

That ruling removes limits on independent expenditures that are not coordinated with candidates' campaigns.