WASHINGTON — A chance encounter with Vice President Dick Cheney at a shopping center in Colorado allowed Steven Howards to express his disgust with the Iraq war and touch Cheney on the shoulder. It also led to Howards’ arrest by Secret Service agents.

Five years later, Howards’ claim that the agents detained him because of his criticism is the subject of a lawsuit that the Supreme Court could hear.

The justices could say today whether they’ll take the case.

The federal appeals court in Denver has said Howards can pursue his lawsuit claiming that he was arrested in retaliation for speaking out. What makes the ruling unusual is that the same court concluded the agents had reason to arrest him for denying that he touched Cheney.

Agents Virgil D. “Gus” Reichle Jr. and Dan Doyle have the support of the Obama administration in arguing they should be shielded from such suits when they have a good reason, or probable cause, to make an arrest.