The obligation of States under international law to act with due diligence does not provide a clear basis for determining the standard of behavior that States should observe when regulating activities subject to their jurisdiction and control. Due diligence remains one of the elusive normative constructs in international law especially in the area of transboundary environmental harm despite conscious jurisprudential attempts to define its scope. This paper contributes to the literature on due diligence as it highlights the normative contours of the due diligence obligation under international environmental law, exploring the various dimensions and implications of this fundamental principle and bringing them to bear with controversial cases such as the Grand Ethiopian Renaissance Dam. Drawing from existing jurisprudence, the paper attempts to provide a glance at the nuances of the due diligence obligation required in the exploitation and management of shared resources while evincing its strengths and frailties.
