"In
Citizens United, the Supreme Court ruled that independent political expenditures by corporations and unions are protected under the First Amendment and not subject to restriction by the government. The Court therefore struck down a ban on campaign expenditures by corporations and unions that applied to non-profit corporations like Planned Parenthood and the National Rifle Association, as well as for-profit corporations like General Motors and Microsoft."
...
"
Any rule that requires the government to determine what political speech is legitimate and how much political speech is appropriate is difficult to reconcile with the First Amendment. Our system of free expression is built on the premise that the people get to decide what speech they want to hear; it is not the role of the government to make that decision for them.
"It is also useful to remember that the mixture of money and politics long predates
Citizens United and would not disappear even if Citizens United were overruled. The 2008 presidential election, which took place before Citizens United,was the most expensive in U.S. history until that point. The super PACs that have emerged in the 2012 election cycle have been funded with a significant amount of money from individuals, not corporations, and individual spending was not even at issue in Citizens United.
"Unfortunately, legitimate concern over the influence of big money in politics has led some to propose a constitutional amendment to reverse the decision. The ACLU will firmly oppose any constitutional amendment that would limit the free speech clause of the First Amendment.
http://www.aclu.org/free-speech/aclu-and-citizens-united