## Facts

- Argentina and Uruguay are parties to the 1975 Statute of the River Uruguay, governing cooperation and environmental protection for a shared boundary river and establishing the Administrative Commission of the River Uruguay (CARU).
- Uruguay authorized, constructed, and operated a major pulp mill (Botnia/UPM) on the River Uruguay.
- Argentina alleged Uruguay unilaterally approved the project without completing the Statute’s prior notification and consultation process through CARU.
- Argentina also alleged the project threatened or impaired water quality and would cause significant transboundary environmental damage.
- Argentina filed an ICJ application under the Statute’s compromissory clause after negotiations failed and sought provisional measures to halt authorizations and construction; the ICJ declined provisional measures in 2006.
- The merits were decided by ICJ judgment on April 20, 2010.

## Issues

1. Whether Uruguay breached the 1975 Statute’s procedural obligations to inform, notify, and consult Argentina through CARU before authorizing the pulp mill.
2. Whether Uruguay breached the Statute’s substantive obligations to protect and preserve the aquatic environment and prevent pollution in the River Uruguay.
3. Whether international law requires an environmental impact assessment (EIA) for projects posing a risk of significant adverse transboundary effects on a shared resource, and what minimum features such an EIA must have.

## Decision

- The ICJ held Uruguay breached the Statute’s procedural regime by failing to comply with required prior notification and consultation steps through CARU before authorizing the project.
- The ICJ held Argentina did not prove Uruguay violated the Statute’s substantive environmental obligations; the Court declined to order dismantling or cessation of the mill’s operations.
- The ICJ stated that, where there is a risk of significant adverse transboundary impact on a shared resource, conducting an EIA is a requirement under general international law.
- The ICJ held an EIA must be undertaken before project implementation, but its content and scope are not fixed by general international law and are determined by domestic law, subject to due diligence.
- The ICJ emphasized the parties’ ongoing duty to cooperate under the Statute, including through CARU and environmental monitoring.

## Legal Principles

- Treaty-based procedural duties of prior notification, information sharing, and consultation in a shared-watercourse regime are enforceable and may be breached independently of substantive environmental harm.
- Breach of procedural cooperation duties does not, by itself, establish breach of substantive obligations to prevent pollution or require dismantling of a completed project.
- Substantive obligations to protect and preserve a shared aquatic environment impose a due diligence standard, requiring reasonable preventive and monitoring measures.
- An EIA is required under general international law when a proposed activity poses a risk of significant adverse transboundary effects on a shared resource.
- An EIA must be performed prior to implementation; absent a treaty standard, the EIA’s detailed content is largely determined by domestic law, constrained by due diligence and the duty to cooperate.

## Conclusion

The ICJ concluded that Uruguay violated the 1975 Statute’s procedural notification-and-consultation framework but that Argentina failed to prove a substantive breach of environmental protection duties, so the mill was not ordered to cease operations; the Court also affirmed that transboundary-risk projects require a prior EIA as a matter of general international law and that both states must continue cooperative monitoring through the river commission.


Pulp Mills on the River Uruguay (Arg. v. Uru.), 2010 I.C.J. 135 (Apr. 20)