That's precisely the paragraph I'm most concerned about. In and of itself, it's open-ended drafting, whereas more modern drafting around the world is becoming much more specific and refined.
The standard referred to there is an open-language standard of customary international law. It comes from—to be precise and lawyer-like—Article 38 of the Statute of the International Court of Justice.
But in interpreting similar language in other treaties in the course of over 600 investment arbitrations, we've seen the standards relating to customary international law and FET vary widely. The standards of proving it vary widely. Even within the NAFTA, there were two cases that came out within eight months of each other—the Glamis Gold and Merrill & Ring—that took exactly opposite approaches under the same treaty. So there is no definition.