I think it's the Tokyo Convention that allows a state that is party to this convention jurisdiction over the aircraft of another state party to the convention in respect of the penal law and any acts that might endanger the aircraft or its occupants (my summary, not the actual legal jargon).
It seems that this incident falls within the parameters of the convention.
I'm certainly not an expert in this field so if I'm wrong with the permitting international law or convention please accept my apologies for misleading.