In a dramatic upheaval that sharply divided the U.S. Supreme Court, a 5-4 majority ruled Thursday that under the First Amendment Congress may not bar corporations and unions from using their own money to make independent expenditures to support or oppose candidates for office.

The Court in Citizens United v. Federal Election Commission (pdf) ruled that the ban on direct corporate expenditures before elections, with criminal penalties, is a powerful chill on legitimate political speech. “Its purpose and effect are to silence entities whose voices the government deems to be suspect,” wrote Justice Anthony Kennedy for the majority. “If the First Amendment has any force, it prohibits Congress from fining or jailing citizens, or associations of citizens, for simply engaging in political speech.”