Sorry, sabenaboy, that which you quote is not legislation.
The Tokyo Convention is very plain, and explains that if the pilot-in-command deviates from an ATC clearance, he assumes responsibility for the safe conduct of the flight.
That's the law.
From where I sit, the Tu154 crew were right, the B757 crew were not, WITH SPECIFIC REGARD TO EXTANT INTERNATIONAL LEGISLATION. With regard to airmanship, the B757 PiC was right. This is my opinion only.
//Start of rant//
ICAO are responsible for some apallingly bad rule-making and 'standardisation'. If we all stop work on safety for a month and simply address ICAO's failings, we have an opportunity for great good. Until we all do, we'll simply be p***ing in the wind for safety.
//end of rant//