A few years ago I went back to the US to visit the crypto museum (incidentally, right across the street from NSA in Fort Meade). It was my first trip to the DC area and the first night I got in, I went over to the Jefferson memorial. A sign on the pathway approaching the dome warns visitors that due to federal law, firearms are prohibited on the grounds.
Jefferson would be proud, I'm sure.
[note to non-US citizens: It's basic right #2 in the USA that people can own and carry firearms.]