Article 20 requires the aircraft not to fly unless it has the required crew on board.
Article 41 requires one pilot to remain at the controls at all times.
Article 29 prohibits the giving of instruction in flying by someone without the correct ratings but then says:-
"(2) This article applies to instruction in flying given to any person flying or about to fly a
flying machine or glider for the purpose of becoming qualified for:
(a) the grant of a pilot’s licence; and
(b) the inclusion or variation of any rating in his licence."
Therefore it appears you can teach your granny to fly so long as that instruction is not for one of the purposes above, you remain at the controls, and you are qualified to fly the thing.
Simple really
Mike