The Federal Election Commission (FEC) and Citizens United have filed their supplemental briefs in Citizens United v. FEC. On June 29 the Supreme Court ordered a rehearing of the case to address whether the Court should overturn two previous rulings. One is the decision in Austin v. Michigan State Chamber of Commerce, ruling that a state ban on corporate spending in election campaigns does not violate the First Amendment. And secondly, McConnell v. FEC, upholding the ban on corporate and labor union spending for electioneering communications.

U.S. Solicitor General Elena Kagan filed a joint motion with former Solicitor General Seth Waxman, representing Senator John McCain (R-AZ) and other sponsors of the Bipartisan Campaign Reform Act. The motion asks that ten minutes of the government's half-hour argument time be allocated to Waxman, arguing on behalf of McCain, Sen. Russ Feingold (D-WI), and former Reps. Martin Meehan (D-MA) and Christopher Shays (R-CT).

Rick Hasen at the electionlawblog.org, has an analysis of the government's brief, and asserts that "the government does not even mention the central holding of Austin, much less defend it." The government's brief argues that the Court should affirm the ruling of the district court, which held that Citizens United should have to abide by disclosure requirements.

Numerous amicus briefs for both sides have been filed, including one from the James Madison Center for Free Speech on behalf of eight former members of the FEC, calling for the overruling of both Austin and McConnell. Most of the amicus briefs are compiled here and available from the FEC.