The plaintiff in this case was arrested by Secret Service agents protecting Vice-President Cheney. After all charges were dropped, he sued the agents claiming that he had been arrested in retaliation for his criticism of the Vice-President, which an agent had overheard. The issue in the case is whether the motive of the agents is irrelevant as long as there was probable cause to arrest. The ACLU amicus brief makes two points: First, the Court should decline to consider the case on the merits because the legal basis for plaintiff’s arrest is unclear on the record. Second, under traditional First Amendment rules, the agents can be held liable if they would not have made the arrest “but for” plaintiff’s constitutionally protected speech.