Why do we have a 'treaty' w/ the Vatican?

Answer 1

Probably because someone from the Bush Administration put pressure on them to sign it or the "terrorists" will get them.

President Clinton had signed the Rome Treaty on 12/31/2000 which showed his support for the International Criminal Court being organized by the United Nations.
http://www.un.org/law/icc/index.html

On September 10, 2001 some Congressperson slid into the record of Congress without reading it words to the effect that the US did not ratify the signature.

According to footnote 7 at the following link
http://untreaty.un.org/ENGLISH/bible/englishinternetbible/partI/chapterXVIII/treaty11.asp

"7. In a communication received on 6 May 2002, the Government of the United States of America informed the Secretary-General of the following:

"This is to inform you, in connection with the Rome Statute of the International Criminal Court adopted on July 17, 1998, that the United States does not intend to become a party to the treaty. Accordingly, the United States has no legal obligations arising from its signature on December 31, 2000. The United States requests that its intention not to become a party, as expressed in this letter, be reflected in the depositary's status lists relating to this treaty."

The Bush Administration has been pressuring the smaller countries to sign bilaterial agreements with the US rather than have the US citizens being subject to International Laws.
http://www.state.gov/s/l/treaty/treaties/2007/section1/index.htm

There is a downloadable listing of all the Treaties at:
http://www.state.gov/documents/organization/83046.pdf

However, I could not find a Treaty for the Vatican.

Answer 2

The Vatican is actually the world's smallest Country. We have treaties with almost all Countries.

Answer 3

We have treates of one sort or another with most countries. The Vatican is an independant nation-state.