In recent years demand has grown for non-state actors to take part in the proceedings of the International Court of Justice (ICJ-CIJ). A similar phenomenon has taken place in the context of other international dispute settlement mechanism, notably in international arbitration and in other economic dispute resolution systems, such as the World Trade Organisation Dispute Settlement Body. Early case law from these institutions indicates the origins of a “move to transparency” which gradually developed into a more accepted practice by adjudicators. The impact of this participation went beyond practice and influenced both the creation new procedural rules and reinterpretation of existing ones. Common aspects of these norms can be a source of inspiration for the ICJ, from which to draw good practices, provided that limits to the comparison between different institutions are respected.