INTRODUCTION

Although the Trail Smelter arbitration has often and justifiably been referred to as the fons et origo of international law on transboundary environmental harm and has over the years attracted considerable attention in the literature, significant differences of opinion, as well as basic misperceptions continue to exist among commentators and experts with respect of the arbitration's true international legal import. Critical views range from outright dismissals of Trail Smelter as of “limited precedential value,” to the belief that, while Trail Smelter recognizes international liability for transboundary damage, it does not impose an obligation to prevent such damage. Similarly, the fact that the Tribunal took a nuanced approach in assessing Canada's liability – setting out the grounds for both a due diligence-based and strict liability argument – appears often to have gone unnoticed. This collection of essays, which seeks to assess for the first time the overall legacy of Trail Smelter and in this process to redress some of the underappreciation of the arbitration's scope and complexity, is thus particularly welcome and relevant.

This paper will not seek to track all the various strands of the Trail Smelter arbitration that have had a discernible impact on the evolution of international environmental law. Rather, its objective is necessarily more modest. Given the assigned topic – the relevance and applicability of Trail Smelter in the context of nuclear energy – this chapter will focus on Trail Smelter's most relevant implication for nuclear power-related activities: a state's obligation to prevent or minimize the risk of transboundary harm.