Answer :
It was to the Congress of the US that the National Rifle Association submit its brief in support of super PACs in Citizens United v. Federal Election Commission.
The correct answer to this open question is the following.
The branch of the federal government that the National Rifle Association submitted its brief in support of super PACs in Citizens United v. Federal Election Commission was the judicial branch.
This case was decided on January 21, 2010. Citizens United wanted the court to issue an order to prevent the application of the Bipartisan Campaign Reform Act on the film, "Hillary: the Movie." The decision of the Supreme Court was to deny the order due to the previous decision in the case of McConnell v. FEC.