When Noriega was holed up in the Vatican Legation in Panama in 1990. He was safe as long as the embassy shield was displayed. When the Diplomatic staff left, they took the shield, and Noriega's protection with it. When they left, the Vatican Legation was just another building,and the U.S. Army could waltz in and detain Ol' Pineapple Face.
I was stationed at the U.S. embassy in Rome 1976-1979. At that time, the U.S. Embassy to the Vatican was a single office, right across the hallway from mine. I never once saw the Ambassador, a member of the Lodge family IIRC. About the time I left, the U.S. Embassy officially opened in the Vatican itself.
interesting stuff, thanks!