Senate Minority Leader Mitch McConnel, R-Ky., is urging the U.S. Supreme Court to safeguard its controversial Citizens United case by overturning a state ruling that defied the high court's decision.Two years ago, a 5-to-4 majority of justices rejected spending limits for corporations and labor unions within federal election law. However, the Montana Supreme Court went in the opposite direction earlier this year and upheld a century-old state law banning corporate campaign spending.Justices Ruth Bader Ginsburg and Stephen Breyer suggested the ruling should be reconsidered given the upheaval against the case, and the high court is contemplating just that.In a legal brief, McConnell joined the U.S. Chamber of Commerce in asking the justices to overturn the Montana decision without holding a hearing. But supporters of the state ruling have also filed a brief urging for a regular review with the justices hearing their arguments.From SCOTUSblog: The new Free Speech for People brief focused specifically on the rise of spending by outside groups and individuals since the Citizens United decision, and contended that that undercut the premises of the decision. "In view of the increasingly dominant role of corporate and private independent expenditures in our electoral politics,” the brief said, “this Court should grant certiorari and reexamine whether its long-standing precedent permitting regulations designed to prevent the use of wealth from drowning out other voices provides an additional basis for upholding restrictions on independent expenditures." That filing also made a broader argument, urging the Justices to use the case as a basis for ruling that corporations are not entitled to the protections of the First Amendment free-speech clause or other provisions in the Bill of Rights.For years, McConnell has been a proponent of free speech for companies in campaign. The GOP leader led the effort to undo campaign finance reform when he filed a lawsuit against the Federal Election Commission.Four votes are needed to review the Montana case while five are needed for a summary ruling that would overturn the state decision without a hearing.