Environmental Law

Trail Smelter Arbitration (United States v. Canada)

3 RIAA 1905

Facts

A large lead and zinc smelter operated at Trail in British Columbia, Canada.
The smelter released sulphur dioxide and other fumes.
Prevailing winds carried smoke southward across the international boundary into Washington State in the United States.
The United States alleged damage to:
crops;
forests;
land;
agricultural productivity.
Canada accepted international responsibility for the private smelter’s conduct under the arbitration agreement.
A tribunal was asked to determine:
whether transboundary damage had occurred;
compensation;
the future operating regime for the smelter.
The dispute produced arbitral awards in 1938 and 1941.

Whether a State is internationally responsible for pollution originating in its territory but causing injury in another State.
What level of proof and seriousness is required.
What compensation and preventive measures should be imposed.
Whether the smelter could continue under a controlled emissions regime.

No State has the right to use or permit the use of its territory in a manner that causes serious transboundary injury in another State.
Responsibility arises where:
the consequences are serious;
the injury is established by clear and convincing evidence.
A State must exercise control over private activities within its territory.
International remedies may include:
compensation for proven past damage;
monitoring;
emission controls;
preventive operating conditions.

The Tribunal relied upon scientific and factual evidence concerning:
sulphur dioxide emissions;
wind direction;
vegetation injury;
periods of greatest exposure.
It found that smoke from the Canadian smelter had caused identifiable damage in Washington.
Canada could not avoid responsibility merely because the smelter was privately operated.
International law deals with the conduct permitted within the State’s jurisdiction.
The Tribunal nevertheless required a relatively high level of proof.
It did not compensate every claimed form of loss.
Claims that were speculative or insufficiently demonstrated were rejected.
For the future, the Tribunal did not permanently close the smelter.
It designed a controlled operating regime based upon:
weather;
seasons;
emission levels;
monitoring.
The smelter’s economic importance was considered, but continued operation was made conditional upon preventing serious transboundary injury.
This connected State sovereignty with responsibility.
A State may use its natural resources, but not without regard to environmental consequences outside its borders.
The case later influenced Principle 21 of the Stockholm Declaration and the modern no-harm principle.

Canada was held responsible for proven damage caused in the United States by emissions from the Trail Smelter.
Compensation was awarded for established injury.
A monitoring and emission-control regime was imposed to prevent future damage.
The decision became the classic authority for the international no-harm principle.
Its formulation was limited to serious injury established by clear and convincing evidence, but its influence extends far beyond transboundary air pollution.
Use this case for: State responsibility to prevent significant pollution from crossing an international boundary.