Section 21.4 "Treaties and Other International Agreements" of The Bluebook: A Uniform System of Citation indicates how to cite various treaty sources. Note that for treaties to which the U.S. is a party, "cite to one of the following sources, listed in the following order of preference: U.S.T. or Stat., T.I.A.S. or T.S. or E.A.S., Senate Treaty Documents or Senate Executive Documents, the Department of State Dispatch, or Department of State Press Releases." If the treaty hasn't yet been published in one of these sources, you may cite to an unofficial source (e.g. ILM or KAV). Foreign treaties are discussed by country in Section "R20: Foreign Jurisdictions."