"Article 5: The aircraft of states, other than scheduled international air services, have the right to make flights across state's territories and to make stops without obtaining prior permission. *However, the state may require the aircraft to make a landing.*"

He seems to be arguing that this clause was broken in spirit or something. I can't quite make out the finer details though, but it's not exactly a slam dunk violation - the treaty does say they may require the aircraft to make a landing and they did.