Opinio Juris highlights an upcoming article on an important issue:

"When is an arbitral panel an international tribunal for purposes of Section 1782? Section 1782, of course, is the statute that authorizes federal courts to order discovery in aid of proceedings before foreign courts and international tribunals. As discussed in a forthcoming article in the Virginia Journal of International Law entitled, Ancillary Discovery to Prove Denial of Justice, what constitutes an international tribunal is not a simple question. It is also a critically important question, because the power to invoke federal court discovery in aid of foreign or international proceedings is one of the most effective evidentiary tools that any international lawyer can wield." 

The post provides a helpful, brief history with useful links. Go there for the specifics and more.