e) their notification to the contracting organizations or to the depositary, if so

agreed.

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 intemational

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 intemational 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 intemational 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 intemational organization may, when s1gnmg, ratifying, formally

confirming, accepting, approving or acceding to a treaty, formulate a reservation unless:

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