The indemnity or compensation referred to in Article 17 shall not be payable:
where the principal has terminated the agency contract because of default attributable to the commercial agent which would justify immediate termination of the agency contract under national law;
where the commercial agent has terminated the agency contract, unless such termination is justified by circumstances attributable to the principal or on grounds of age, infirmity or illness of the commercial agent in consequence of which he cannot reasonably be required to continue his activities;
where, with the agreement of the principal, the commercial agent assigns his rights and duties under the agency contract to another person.