23. (1) A relevant decision which is made within the scope of a registered co-decision-making agreement shall not be challenged on the grounds that the appointer did not have the capacity to make the decision.

(2) Where a co-decision-making agreement stands registered, a relevant decision made otherwise than jointly by the appointer and the co-decision-maker is null and void.

(3) (a) Subject to paragraph (b), where a relevant decision requires the signing of any document, the relevant decision is null and void unless both the appointer and the co-decision-maker sign the document.

(b) Where the appointer is unable to make his or her signature, a document may be signed on the appointer’s behalf by a person who has attained the age of 18 years and who is not the co-decision-maker if the appointer is present and directs that the document be signed on his or her behalf by that person.