I wore a sword at the time and no one had an issue with it.

Carrying a sword is, to the best of my internet research, perfectly legal in DC. Switchblades and concealable knives are right out (as well as it retroactively becoming illegal to carry the sword if they can demonstrate an intent to use it to harm someone.) Carrying a firearm is pretty tricky (and forbidden in federal buildings or in the middle of demonstrations).

That is, a sword is treated as a prop and a gun/switchblade/brass knuckles etc. are treated as weapons.