A director can sign, based on the executive powers granted to him by the Articles of Incorporation of the company. In case if this position is filled by the beneficial owner himself, or by his appointee, this signatory right is apparently unconditional. If the director is in fact a third-party director, then he would only sign if express instructions or authorizations to do so are issued by the beneficial owner. Under no circumstances would a nominee director be entitled to sign without such instructions, as it would be contrary to his mandate and the Terms and Conditions of our business with the client.
Finally, a person who is holding a valid Power of Attorney can sign on behalf of the company, within the limitations contained in the scope of that Power of Attorney. It is quite common that the beneficial owners or their appointees execute signatory powers on behalf of an offshore company through the rights granted by a Power of Attorney.