The ICJ Statute is set to ensure that in the Court as a whole "the main forms of civilization and ... the principal legal systems of the world" find themselves duly represented. (1) In practice, this leads to some sort of balance between judges educated in the civil law and those educated in the common law. During my nine years at the Court, I have always been surprised at how rare it was that differences based on these legal traditions came to the fore. But they do so, if only occasionally, and where they appear they almost always turn on questions of procedure, here again on matters of evidence.
The one such "clash of (legal) civilizations" that impressed me most strongly was related to the handling by the Court of scientific evidence in the Pulp Mills case brought by Argentina against Uruguay in 2006 and decided four years later. (2) I would submit that the difference had to do with views on the management of what I would call civil litigation, or a civil procedure, before and in the Court (ICJ proceedings certainly bearing distinct civil-procedural rather than criminal- or administrative-procedural features).
In a nutshell, and perhaps a bit oversimplified, the case arose out of a project, authorized by Uruguay, for the construction of two (later, one) huge pulp mills situated on the like-named river forming the boundary with Argentina. Argentina claimed that the operation of the mill would lead to considerable pollution of the River Uruguay and thus to all sorts of negative consequences, which would breach a treaty concluded between the two countries in 1975 specifically for the protection and preservation of the river. In contrast, Uruguay tried to convince the Court that the operation of the plant did conform to the highest (i.e., EU) standards and best practices of the industry.
As expected, both parties produced large amounts of scientific expert evidence, both in their written pleadings and in the oral hearings. (3) Confronted with the mass of such highly complex technical material, I found myself simply not feeling capable of drawing the necessary legal conclusions, for instance on the severity and thus relevance of the emission of certain noxious substances for water pollution. To give a few examples, I had no clue as to the effects of the breakdown of nonylphenolethoxylates; the binding of sediments to phosphorus; the possible chain of causation leading to algal bloom or dioxin/furan pollution; how to assess whether two- or rather three-dimensional modeling was the most...