For example;
War crimes, as defined by the Rome Statute of the International Criminal Court...
OR
War crimes, as defined by the Rome Statute of the International Criminal Court...
For example;
War crimes, as defined by the Rome Statute of the International Criminal Court...
OR
War crimes, as defined by the Rome Statute of the International Criminal Court...
@Anyon provides the normative answer, but I want to provide a different perspective. You probably spent twenty minutes thinking about the issue and another ten writing the post here. With clicking "Refresh" a number of times to see what people write, and other distractions, you will have spent an hour on this one issue.
This is not a good use of your time. Style guides are there to make it easier for readers, and to provide uniformity. But in cases where it's a one-off -- we don't reference treaties all that often, and the fact that you didn't know what to do means that your readers likely won't have a definitive stance on it either -- a reasonable strategy would be to pick a style for your paper and be consistent about it. Then move on. In that hour, you could have written a page or two; instead, you worried about an entirely unimportant question -- there are better things you can do!
Not as a matter of course. The 16th Edition of the Chicago Manual of Style itself does not italicize treaties.
8.79 provides several examples of "Formal or accepted titles of pacts, plans, policies, treaties, acts, programs, and similar documents or agreements" that, notably, are all set in Roman type. International examples include (formatting preserved)
- Treaty for the Renunciation of War, known as the Pact of Paris or the Kellogg Briand Pact; the pact
- the Treaty of Versailles; the treaty
- the Treaty on European Union (official name); the Maastricht treaty (informal name)
Elsewhere, 14.302 states that, in the bibliography,
Titles of treaties are set in roman and capitalized headline-style (recall that The Bluebook capitalizes prepositions of more than four letters). An exact date indicates the date of signing and is therefore preferable to a year alone, which may differ from the year the treaty was published in one of the works above. Page numbers are given where relevant.