"We need to work with some other country...like Taiwan, or some other...and introduce a treaty to pull out of the UN. Boy would the fur fly over that!" Problem is it is not so easy to break the San Francisco Treaty that formed the UN in a official capacity. The world would cry fowl play. And don't they actually owned the land at this point? I believe clever John D. Rockefeller provided the land with legals to make it UN property. If so, how do you boot em off our shores?
Emminent domain...hehehe! Put an anti-terror HQ there for Homeland Security. Pay them for the land and send them packing.