Article 17
Consent to be bound by part of a treaty and choice
of differing provisions
1. Without prejudice to articles 19 to 23, the consent of a State or of an international organization to be bound by part of a treaty is effective only if the treaty so permits, or if the contracting States and contracting organizations or, as the case may be, the contracting organizations so agree.
2. The consent of a State or of an international organization to be bound by a treaty which permits a choice between differing provisions is effective only if it is made clear to which of the provisions the consent relates.
Article 18
Obligation not to defeat the object and purpose of
a treaty prior to its entry into force
A State or an international organization is obliged to refrain from acts which would defeat the
object and purpose of a treaty when:
(a) that State or that organization has signed the treaty or has exchanged instruments constituting the treaty subject to ratification, act of formal confirmation, acceptance or approval, until that State or that organization shall have made its intention clear not to become a party to the treaty; or
(b) that State or that organization has expressed its consent to be bound by the treaty, pending the entry into force of the treaty and provided that such entry into force is not unduly delayed.
SECTION 2. RESERVATIONS
Article 19
Formulation of reservations
A State or an international organization may, when signing, ratifying, formally confirming, accepting, approving or acceding to a treaty, formulate a reservation unless:
(a) the reservation is prohibited by the treaty;
(b) the treaty provides that only specified reservations, which do not include the reservation in question, may be made; or
(c) in cases not falling under subparagraphs (a) and (b), the reservation is incompatible with the object and purpose of the treaty.
