Treaty Interpretation and the Reservations Problem
A multilateral environmental treaty permits reservations 'unless incompatible with the object and purpose of the treaty'. State A deposits a reservation excluding the treaty's dispute-settlement clause. State B objects, arguing the reservation is incompatible with the object and purpose because the treaty's effectiveness depends on binding dispute settlement. State C objects but does not oppose the treaty's entry into force between itself and State A. A fourth state, D, remains silent. State A then invokes the reservation to refuse arbitration. The treaty has 60 parties; the dispute concerns transboundary harm affecting State B and State C. Your government must decide whether to (i) accept the reservation, (ii) object with opposition to entry into force, or (iii) object without opposing entry into force, and must assess the legal effect of each choice on the dispute.
1. Analyse the legal effect of the options available to your government.
Read the worked answer
Under the law of treaties, a reservation incompatible with the object and purpose is impermissible, but the consequence is contested. Option (i), acceptance, precludes later objection and locks in the reservation's effect between the parties. Option (ii), objection with opposition to entry into force, means the treaty does not enter into force between the two states, which removes the treaty basis for the dispute but may leave customary law and general dispute-settlement routes available. Option (iii), objection without opposing entry into force, is the most common: the treaty enters into force but the reserving provision does not apply between the parties, so the dispute-settlement clause may still bind State A vis-à-vis your state. State C's position illustrates option (iii). State D's silence, after twelve months, is deemed acceptance. The tested judgement is that objecting is not enough; the objecting state must choose whether to oppose entry into force, because that choice determines whether the dispute clause survives. Your government should prefer option (iii) if it wants the dispute clause to apply, and should state the legal basis explicitly.
2. State A argues that because some parties accepted the reservation, it is valid erga omnes. Evaluate.
Read the worked answer
The argument is unsound. Acceptance by some parties affects the reservation's effect only between those parties; it does not cure an impermissible reservation for all. Validity against the object-and-purpose test is assessed objectively, and acceptance by a subset cannot convert an impermissible reservation into a permissible one erga omnes. However, the practical consequence is fragmented: between State A and accepting states the reservation operates; between State A and objecting states that opposed entry into force, no treaty relation arises; between State A and objecting states that did not oppose entry into force, the reserved provision is inapplicable. Your government should therefore reject the erga omnes claim while recognising that the treaty regime may be fragmented. The tested skill is distinguishing the validity question from the effects question and resisting a rhetorical overgeneralisation.