International institutions, with a few minor and ad hoc exceptions, are firmly grounded in treaties that establish their objectives, conditions of membership, and internal and external operational parameters. These treaties are binding on their party members and, perhaps – in the instance of near-universal organizations – also on nonmembers.

It could be argued that it little matters whether such an institution's foundational instrument is regarded as a constitution. Yet leading thinkers, such as the authors of this volume, seem to think the issue is worth serious examination. They express strongly held views as to why the issue is important and argue that how it is answered can have a significant impact on the role and operation of leading international organizations.

An international organization grounded in a constitution, they believe, has a different gravitas from the many purely ad hoc reciprocal arrangements made for the passing convenience of states.

The authors of these chapters do not merely note the phenomenon of greater gravitas but also explore how constitutionalization affects the practice of an institutionalized system of cooperation. For one thing, it determines how the institution absorbs the need for change. Whereas a constitutionally based system accommodates and adapts to its own practice, lesser consensual arrangements tend to insist on strict literal construction of their terms and resist their transformation through interpretative practice.

The problems of the Secretary-General are as many as the number of member states of the United Nations. Although the UN Charter merely designates him or her “the chief administrative officer of the Organization” the position, as this volume has shown, is both much more and much less than that. In the vexed, and too often adversarial, relationship of the office to the members of the organization, the Secretary-General is sometimes treated as an errand boy and punching bag. This is partly the fault of short-sighted foreign offices, but also of the contradictions in the way the job is described in the Charter. That instrument seems to establish him or her as an important independent force, but also as a mere servant of the political organs of the organization. The problems that have afflicted the various incumbents mostly result from those contradictory designations.

Yet this is not the only contradiction of the office. Quite apart from whether the Secretary-General is intended to be a secretary or a general, the appointment process is designed to avoid selecting either: it is a political rather than professional process, but one that is geared to choosing the weakest rather than the strongest candidate. This is not to disparage the various incumbents, but, as Brian E. Urquhart recounted in chapter 1, those who have stood tallest in the role have been those who most exceeded expectations.

Even within the two dominant functions of the position, the Secretary-General frequently lacks sufficient internal authority to be an effective administrator of the organization, while also lacking the resources to exercise his or her external functions with credibility.

Non-lawyers tend to have greater reverence for the law than do lawyers, perceiving it in almost Hammurabic or Mosaic terms: written in stone and authored by supreme authority. In this, they may reflect the views of those seventeenth- and eighteenth-century legal philosophers who regarded law as the inspired human embodiment of divine wisdom and morality or of those nineteenth-century positivists who understood law to be the commands of supreme rulers.

Beginning in the twentieth century, however, law has come to be understood in less absolute and more dynamically transactional terms, as a system of norms constantly engaged in a process of challenge, adaption, and reformulation. This more contingent view of law may be merely another manifestation of the transformation of the command structure of social order that has come about as a result of political liberalization.

International law has not escaped this changing ethos. Indeed, as law in general has come to be understood less as an ineluctable command and more as part of liberal discourse – and as only one of many instruments of social stabilization and change – so, too, has the perception of international law changed. In the twenty-first century, it has become professionally respectable for practitioners of both domestic and international law, when asked whether a proposed course of conduct is lawful, to reply that, well, sometimes it is, sometimes it isn't, and sometimes it both is and isn't.

The legacy of Sir Hersch Lauterpacht

When, in 1933, Judge Lauterpacht wrote The Function of Law in the International Community, he reasoned from first principles that the world's legal system must be grounded in an absolute rule: “There shall be no violence” by states. He described this as the “primordial duty of the law.”

At the same time, he concluded prophetically that the League of Nations' Covenant would fall far short of establishing that rule in law, let alone in fact. It was full of loopholes for aggressors and their appeasers. Loopholes drew his scorn. “It is impossible,” he observed, “in the scheme of things devised to secure the reign of law, to provide machinery calculated to disregard the law …”

Loopholes, as we shall see, are the subject of this study, which will argue that they can be bad, but that they also have an important role to play in saving law from itself.

After the Second World War, with Lauterpacht's participation, the Nuremberg tribunal was called upon to draw a much brighter line than hitherto against aggression. So, too, at Dumbarton Oaks and San Francisco, a UN Charter was written that makes absolute the obligation of states not to resort to force against each other and to resist collectively any breach of this prohibition.

New remedies, as we know from medicine, tend to produce unexpected side effects. Article 2(4) of the Charter seemingly cures the Covenant's normative ambiguities regarding states' “threat or use of force” against each other.

The “self-help” dilemma

When a right is denied, it is natural to turn to the authority that is the source of that right in the expectation that it will be enforced. When that expectation is not met, there is moral force to the argument that those aggrieved by the failure should themselves be allowed to enforce their legal entitlement as best they can.

In international law, the issue of the legality of countermeasures and self-help arises when, a state having refused to carry out its legal responsibilities and the international system having failed to enforce the law, another state, victimized by that failure, takes countermeasures to protect its interests. “Its interests” in this context denotes the peaceful enjoyment of rights accruing to a state, of which it is deprived by the continuing wrongful acts of another state. It may also be, however, that the notion of a transgressed state interest has expanded to include not only violations of its rights as a sovereign, but also of rights held derivatively as a member of the international system. Thus, for example, every state may enjoy the right erga omnes not to have the earth's “commons” – the seas, the air – polluted in violation of globally applicable norms. Along similar lines, every state may have a right to act to prevent a genocide that, even if not directed at its own people, violates the treaty-based common conscience of humanity.

When does a state's recourse to force violate its legal obligations under the UN Charter? Does the answer lie exclusively with the black-letter text of Article 2(4), or is the practice of UN organs and of the constituent states also relevant?

In its judgment in the Nicaragua case, the World Court set out its view on the interaction between practice and the legal norm pertaining to armed intervention:

True, practice cannot by itself amend a treaty, but, as the Court has also pointed out, the practice of a UN organ may be seen to interpret the text and thereby to shape our understanding of it. Persons other than lawyers may, however, be forgiven for thinking this a distinction without much difference. Whether its effect is characterized as modification or interpretation of text, practice matters.

This is particularly so when strict construction of treaty text leads to a reductio ad absurdum.