Corporate political spending is free speech.
Justice Scalia wrote the concurrence on Citizens United v. Federal Election Commission on Jan 21, 2010:
Prior to the 2008 primary elections, Citizens United, a nonprofit corporation dedicated to educating the American public about their rights and the government, produced a politically conservative 90-minute documentary entitled Hillary: The Movie. This documentary covers Hillary Clinton’s record while in the Senate & the White House. However, The Movie falls within the definition of “electioneering communications” under the Bipartisan Campaign Reform Act of 2002 (“BCRA”)–a federal enactment designed to prevent “big money” from unfairly influencing federal elections–which, among other things, prohibits corporate financing of electioneering communications. The FEC [enforced the provision] of BCRA prohibiting corporations from broadcasting electioneering communications within 60 days of a general election. [The Supreme Court rules that this] violates the free speech clause of the First Amendment.
Justice Kennedy , Opinion of the Court (Roberts, Scalia, Alito, and Thomas concurring):
Some members of the public might consider “Hillary: The Movie” to be insightful and instructive; some might find it to be neither high art nor a fair discussion on how to set the Nation’s course; still others simply might suspend judgment on these points but decide to think more about issues and candidates. Those choices and assessments, however, are not for the Government to make.
Justice Stevens (dissent joined by Ginsburg , Breyer, and Sotomayor)
Neither Citizens United’s nor any other corporation’s speech has been “banned.” All that the parties dispute is whether Citizens United had a right to use the funds in its general treasury to pay for broadcasts during the 30-day period. The notion that the First Amendment [allows that] is, in my judgment, profoundly misguided. Although I concur in the Court’s decision to sustain BCRA’s disclosure provisions, I emphatically dissent from its principal holding.