DENVER  Former Vice President Dick Cheney will have to give his account  under oath, in a legal deposition  of what happened at a Colorado ski resort in June 2006 when a man stepped up to protest the Iraq war and was arrested, a federal district judge ruled Monday.

The protester, Steven Howards, sued five Secret Service agents in Mr. Cheney’s security detail after the encounter at the Beaver Creek resort. Mr. Howards’s lawyers have argued that Mr. Cheney’s version of events is crucial to getting at the truth.

Mr. Cheney’s lawyers had responded  successfully until Monday’s ruling by Judge Christine M. Arguello in Denver  that a deposition was unnecessary. A federal magistrate agreed with Mr. Cheney last April; Judge Arguello’s ruling reversed that decision.

Mr. Howards has admitted to approaching Mr. Cheney and saying the administration’s policies in Iraq were disgusting, or words to that effect. He walked away unhindered by Secret Service agents, but he was arrested by them about 10 minutes later for what they said was the “assault” on the vice president.