The United States Constitution, and nearly all state constitutions, have clauses that protect lawmakers from arrest during legislative sessions, and while traveling to and from them. Historians say the privilege dates to the early 1600's in England, when the Stuart kings were fighting Parliament and sheriffs would lock up members while they were home for the weekend.

Virginians learned the lesson in 1676 when Nathaniel Bacon, who led a rebellion against the Colonial policies of Gov. William Berkeley, was fired upon and arrested on the Governor's orders while trying to take his seat in the House of Burgesses.

Flash forward to this February, when the delegate, Robert E. Nelms, Republican of Suffolk, was arrested in Byrd Park, four miles from the Capitol, three hours after the session had ended for the day. In Byrd Park last year, police made 186 arrests for lewd acts, more than twice as many as in any other park in the city.

Four years ago, Mr. Nelms was robbed after dark in the same park. At the time, he said he was exercising. This time, he said he was urinating when an undercover officer happened upon him on a wooded path.

Although no evidence has been presented against Mr. Nelms, the circumstances were so suspicious that legislators spent the rest of the past winter session trading quips and limericks about the incident.