A special headquarters agreement, signed by Secretary-General Trygve Lie and US secretary of state George C. Marshall at Lake Success on 26 June 1947, has been in force since 21 November 1947.
It defines the 18 acres of land in New York City located between 42nd and 48th Streets and First Avenue and the Franklin D. Roosevelt Drive as the Headquarters District of the United Nations.
Subsequently, by supplemental agreements between the UN and the US, additional office space located in buildings in the vicinity has been included in the Headquarters District.
The Headquarters District is "under the control and authority of the United Nations as provided in this agreement."
It is the seat of the UN, and the agreement stipulates that the district "shall be inviolable."
Federal, state, and local personnel on official duty may enter it only with the consent of the Secretary-General.
The UN may make regulations for the area.
US federal, state, and local law, insofar as it is inconsistent with UN regulations, does not apply here; otherwise, the US courts would have jurisdiction over actions and transactions taking place in the Headquarters District.
Read more: http://www.nationsencyclopedia.com/United-Nations/United-Nations-Headquarters-HEADQUARTERS-AGREEMENT-BETWEEN-THE-UN-AND-THE-US.html#ixzz4U8zx62XF
That's all true, but somewhat irrelevant. The Constitution, laws, and treaties (ratified by the Senate) are the supreme law of the land. A "special headquarters agreement" signed by the U.N. and Marshall only has whatever force is granted to it by Congress by statute. In other words, a new Congress and President are perfectly free to pass whatever laws they wish modifying or even eliminating that relationship. And even if there was a formal treaty granting that land to the U.N., we would still be within our sovereign rights to withdraw from that treaty any time we wished. In fact, a President can withdraw from a treaty without even obtaining approval of the Senate -- recall Carter unilaterally abrogating the mutual defense treaty with the Republic of China.
In other words, the control we have given to the U.N. over that property neither permanent nor inviolate. If we want them gone, there are perfectly easy, legal ways for us to do that. And if your link is correct/complete (it doesn't cite to any
statutes), then the U.N. mission is entirely a creation of (essentially) an executive order/determination, and its authority over that land could be reversed by a new President on Day 1 if he so chose.
I'm not saying he
should do that, but I also see no harm in a new Administration casually reminding folks of that fact.
@thackney