Burns Law Library Q&A

The rule for citing multilateral treaties for which the U.S. is a party can be found in Rule 21.4.5(a)(ii) of The Bluebook, which references a list of official U.S. sources to cite. You then want to consult the State Department's Treaties in Force, which identifies where US treaties are published.

Here, the Treaties in Force shows that NAFTA has never appeared in either of the State Department's official publications: Treaties and Other International Acts (TIAS), or United States Treaties and Other Agreements (U.S.T.).

Rule 21.4.5(a)(i) lists Senate Treaty Documents as the next acceptable source. NAFTA (short for the North American Free Trade Agreement) is a unique case in that it was submitted to both the Senate and House under the fast-track procedure, so it was published as a House Document (H.R. DOC. NO. 103-159, vol. 1) rather than a Senate treaty document. 

When no source listed under Rule 21.4.5(a)(i) has published the treaty, Rule 21.4.5(c) should be consulted next, which permits the use of an unofficial source, International Legal Materials (ILM). Therefore, the citation would be:

North American Free Trade Agreement, Can.-Mex.-U.S., Dec. 17, 1992, 32 I.L.M 289 (1993).

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