SCOTUS has granted certiorari to consider such questions and to determine whether an arrest is invalidated when made in retaliation for the exercise of free speech. The case is Reichle and Doyle vs Howards.
Back in 2006, a Colorado man took his son to a piano recital in the Beaver Creek resort area when he saw the former Vice President, Dick Cheney, emerge from a shopping center and begin speaking to bystanders. This man, Steven Howards, drew the attention of Cheney's nearby secret service detail when he said into his cell phone he was going to ask Cheney how many kids he killed today.
When it was his turn to greet the VP, Howards told Cheney that his Iraq policy was "disgusting". As Cheney was turning away from the man, Howards allegedly reached out and touched Cheney on the shoulder, thereby engaging the secret service detail, who detained him for questioning and eventually arrested him for assault.
In a civil rights lawsuit subsequently filed in federal court, Howards claimed that his arrest violated his right to free speech under the First Amendment to the U.S. Constitution. The secret service agents asserted governmental immunity but the Denver-based Tenth Circuit Court of Appeals disagreed, holding that Howards' case should proceed on the basis that law enforcement officers cannot make an arrest based on the exercise of an individual's right to free speech.
For their part, the government asserted that the simple assault on Cheney was sufficient to make the arrest. Also, the government asserts a public policy interest in supporting secret service officers' need to make split-second decisions without having to second guess the liability implications of their actions.
The case will be scheduled for oral argument sometime in March or April 2012. Justice Kagan will not take part, presumably due to her involvement in the case when she served as the U.S. Solicitor General.