WASHINGTON -- The U.S. Supreme Court on Monday struck down Montana's century-old limits on corporate political spending, putting an end to the state's resistance to Citizens United and effectively expanding that controversial ruling to the state and local elections.

Citizens United v. Federal Election Commission, decided in January 2010, struck down federal limits on campaign spending by corporations and unions as violations of the First Amendment. Justice Anthony Kennedy, writing on behalf of Chief Justice John Roberts and Justices Antonin Scalia, Clarence Thomas and Samuel Alito, reached the bold conclusion that "independent expenditures, including those made by corporations, do not give rise to corruption or the appearance of corruption," and therefore "[n]o sufficient governmental interest justifies limits on the political speech of nonprofit or for-profit corporations."

In December 2011, the Montana Supreme Court disagreed. It found that the state's Gilded Age history of business-driven corruption was sufficient to justify the state's Corrupt Practices Act. Passed by voter referendum in 1912, the law decrees that a "corporation may not make ... an expenditure in connection with a candidate or a political party that supports or opposes a candidate or a political party."

By summarily reversing the case, American Tradition Partnership v. Bullock, the justices refused to reconcile their sweeping statement of free speech principles in Citizens United with the real-world facts -- from Montana's history to today's super PACs -- put forward by Montana and its supporters to demonstrate that independent expenditures do, indeed, corrupt or create the appearance of corruption. Instead, the 5-4 majority, in an unsigned opinion, wrote that "[t]here can be no serious doubt" that Citizens United applies to Montana's law.

"Montana's arguments in support of the judgment below either were already rejected in Citizens United, or fail to meaningfully distinguish that case," the majority wrote.

Justice Stephen Breyer, joined by Justices Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan, wrote to dissent from the summary reversal. "Montana's experience, like considerable experience elsewhere since the Court's decision in Citizens United, casts grave doubt on the Court's supposition that independent expenditures do not corrupt or appear to do so," Breyer wrote. "Were the matter up to me, I would vote to grant the petition for certiorari in order to reconsider Citizens United or, at least, its application in this case."

CORRECTION: A previous version of this post incorrectly referred to Montana as "The Granite State," which is in fact New Hampshire.