Firearms Not Banned Everywhere in DC

“The regulation on the grounds here is that a member can keep a firearm [handgun, shotgun or rifle] within the confines of his office,” .... “D.C.’s laws don’t apply on Capitol grounds.”
Many members of Congress aren’t aware of the House regulations, which have been in place for more than 40 years...
“Well, it’s not something that’s advertised,” 
TheHill.com - Lawmakers say they won't pack heat.