ABSTRACT
The transboundary harm principle was most recently discussed in the context of the San Juan River case. One of the oldest and central principles of international environmental law is the transboundary harm principle. The Court found that the construction of the road posed a risk of 'significant transboundary harm' and as such Costa Rica was under an obligation to carry out an environment impact assessment (EIA) or to consult with Nicaragua about the project. This Court cannot continue to narrowly interpret the transboundary harm principle to ignore larger, more global and complex implications of activities for States as a whole, but Planet Earth as well. The premise behind the transboundary harm principle is that States must 'protect' the territory of neighbouring States from harm resulting from activities that they control. The Court erred in continuing to rely on a narrow reading of the transboundary harm principle.
