Burns Law Library Q&A

The rule for citing multilateral treaties for which the U.S. is a party is found in Rule 21.4.5(a)(ii) of The Bluebook which references a list of official U.S. sources to cite to from section (a)(i) of that same rule.

Next, consulting the State Department's Treaties in Force, it can be determined that the International Covenant on Civil and Political Rights (ICCPR) has never appeared in the State Department's official publications of treaties entitled United States Treaties and Other International Agreements (U.S.T) or Treaties and Other International Acts (TIAS).

Therefore, moving down the remaining list of acceptable sources in Rule 21.4.5(a)(i), the United Nations Treaty Series (UNTS) is next on the list of acceptable sources. The ICCPR was published in the United Nations Treaty Series at 999 U.N.T.S. 171. 

The ICCPR was also published as a Senate Executive Document: S. Exec. Doc. No. E, 95-2. 

For more information about treaty research see A Guide to Treaty Research or the Treaties and International Agreements guide.