While it is generally agreed that international liability should not arise unless there is a breach of duty, further inquiry is necessary in relation to the specific duties on the part of States to prevent, control, and reduce transboundary damage.1 In this regard, the most important such duties are encapsulated by the doctrine of due diligence.
The doctrine of due diligence is often said to have originated in English common law tort actions for negligence, although as a general concept it cannot be characterized as belonging to any one legal system or tradition. It is occasionally invoked by analogy in international jurisprudence.2 In the Alabama Arbitration of 1872 between the United States and the United Kingdom over the alleged failure of the United Kingdom to fulfill its duty of neutrality during the American Civil War, the notion of due diligence was considered by the Tribunal, which stated:
1 With regard to the maxim sic utere tuo alienum non laedas, one author commented: “this maxim does not contain a principle of unambiguous content generally recognized at the national level and/or by States in their mutual relations and should, for the sake of clarity of legal argument, therefore be avoided in discussions about the rights and duties of States” concerning shared resources: J. G. Lammers, “Commentary on Papers Presented by Charles Bourne and Alberto Szekely,” Colorado Journal of International Environmental Law and Policy (1992), vol. 3, p. 103, at p. 104.
2 For example, in consideration of State responsibility for the protection of aliens or foreign interests, Eagleton said: “the duty of prevention is not of course, an absolute one. Whether the State has fulfilled its obligations in this regard is measured by the rule of due diligence”: Clyde Eagleton, The Responsibility of States in International Law (New York, New York University Press, 1928), p. 88.