2.3. Article 19 of the VCLT: different scenarios
Subparagraph a. Reservations prohibited by the treaty
The purpose of, for example, multilateral anti-pollution treaties, sometimes requires the prohibition of reservations. Another means of establishing consensus is, in that case, the CBDR: Common But Differentiated Responsibility Principle. Differentiation between states' obligations is deemed tolerable.
Subparagraph b. Only specified reservations may be made or certain reservations are prohibited by the treaty
With reference to human rights treaties, the ECHR of 1950 concludes that reservations are allowed, unless the reservation is incompatible with a particular provision and the reservation is of a general character (art. 57 ECHR relating to art. 19 VCLT). This is pretty much the same criterion as would be applied to the 1951 case.
Subparagraph c. The treaty remains silent on reservations
Read the more extensive "Reservations to the Convention of Genocide, Advisory Opinion, ICJ Reports of 1951, page 15". As I've mentioned before, the conclusion reads that "..reservations are allowed in principle, unless sub-para a or b applies, or unless the reservation is contrary to the object and purpose of the treaty in question (art. 19 (c) VCLT)".
Remark that these provisions on reservations apply to multilateral treaties. If a reservation refers to a bilateral treaty, a revision of the treaty in question or its components may be required.
2.4. Acceptance of and objection to reservations (art. 20 VCLT)
1. the first way to "permit" a reservation could not be any more clear: as article 20, para 1 of the VCLT reads, a reservation expressly authorized by a treaty does not require any subsequent acceptance by other contracting States, unless the treaty so provides. This must be the ideal scenario;
2. according to the 2nd paragraph, a reservation requires acceptance by all parties, when it appears from the limited number of negotiating States and the object and purpose of a treaty, that the application of the treaty in its entirety between all the parties is an essential condition of the consent of each one to be bound by the treaty;
3. when a treaty is a constituent instrument of an international organization and unless it otherwise provides, a reservation requires the acceptance of the competent organ of that organization.
2.4.1. Scenarios involving the acceptance of or objection to reservations
Problems arise when the treaty does not provide any means of acceptance or when none of paragraphs 1 to 3 are applicable. To determine whether a reservation is compatible with the object and purpose of a treaty, each treaty partner has to decide on the acceptance of and objection to reservations.
From art. 20 para 4 and 5 VCLT follows that:
a. Another contracting State can expressly accept the reservation, which constitutes the reserving State a party to the treaty in relation to that other State when the treaty is in force for those States.
b. An objection made by another contracting States, does not preclude the entry into force of the treaty as between the objecting and reserving States, unless a contrary intention is definitely expressed by the objecting State.
Thus, despite the objection, the reservation will enter into force between the reserving and objecting States, as long as the objecting State does not expressly discard treaty relations with the reserving State.
c. An act expressing a State's consent to be bound by the treaty and containing a reservation is effective as soon as at least one other contracting State has accepted the reservation.
d. A contracting State remains silent. According to paragraph 5, a reservation is considered to have been accepted by a State if it shall have raised no objection to the reservation by the end of a period of twelve months after it was notified of the reservation, or by the date on which it expressed its consent to be bound by the treaty, whichever is later.
2.5. Acceptance of or objection to reservations in relation to its legal effects
A summary of the legal effects of acceptance of or objection to reservations:
1. Whether the Accepting State expressly or silently accepts the reservation (implicit acceptance = art. 20(5) VCLT), art. 20(4)(a) and art. 21(1) VCLT do apply. The legal effect is that a treaty has been established between the Reserving and Accepting State and that either of the parties to the treaty can invoke the reservation;
2. If a contracting State does object to a reservation, but does not wish to discard treaty relations with the Reserving State (art. 20(4)(b)), the provision to which the reservation relates, does not apply between parties to the extent of the reservation, as art. 21(3) VCLT prescribes the legal effect of the objection;
3. The fourth scenario is that a State objects to a reservation and discards treaty relations with the Reserving State, art. 20(4)(b). The treaty does not enter into force between the Reserving and Objecting State, the latter ultimately not being a "contracting" party to the treaty.
