This chapter examines the ICJ’s influence on international environmental law. Drawing on concrete examples, the author identifies six ways in which the Court’s jurisprudence has contributed to environmental law: by articulating foundational principles; by acting as a gatekeeper for customary international law; by elaborating existing principles; by interpreting environmental agreements; by valuing environmental harms; and by incorporating environmental considerations into other areas of international law. The author reflects on potential future evolutions of the Court’s role in the international environmental law space, given the increasing number of disputes that the Court has addressed in this field in recent years.

A growing number of states have started pointing to the customary doctrine of countermeasures as the most feasible unilateral remedy in the case of a malicious cyber operation carried out by an adversarial actor. Thus, the legal requirements of successfully invoking a right to resort to countermeasures are analysed in depth. In particular, the chapter deals with state policies such as 'active cyber defences' and 'hacking back' as reactions to cybersecurity incidents, and their lawfulness as countermeasures. After examining the pervasive problem of attribution in cyberspace, the states' duty to prevent malicious cyber operations emanating from their territory and the standard of due diligence in this regard are investigated. The chapter concludes with considering the invocation of countermeasures for the purpose of guarantees of non-repetition and reparation in the aftermath of a cybersecurity incident.