International Common Law: The Soft Law of International Tribunals

I. INTRODUCTION The dominant trend in international law since the end of the Second World War has been one of increasing legalization.1 States have created legal regimes of one form or another to govern a host of areas previously left to the realm of politics. Not surprisingly, this rising tide of legalization has confronted states with the problem of designing legal mechanisms to address heretofore political problems. But states can be innovative, and the novel application of legal solutions to political problems has led to a proliferation of new or rarely used forms of international law. States have expanded the use of international organizations,2 created international tribunals with jurisdiction over a range of both state and individual conduct, and employed soft law to establish rules in a wide range of issue areas.4 The subject of this Article lies at the intersection of two institutions states have used during this period of legalization: international tribunals and soft law. We argue that the nature of channeling legal disputes to international tribunals necessarily implicates the use of soft law. In short, decisions of international tribunals interpret binding legal obligations but are not themselves legally binding beyond the particular states and the particular facts before the tribunal. Any further role performed by these decisions is best characterized as soft law. Tribunal rulings can nevertheless influence state behavior by implicating a state's reputation for compliance with international law, by bolstering the reciprocity underlying an agreement, or by triggering retaliation.5 Moreover, by establishing a tribunal to interpret legal obligations in a way that gives rise to a soft-law jurisprudence, states are able to expand the tribunal's influence beyond those states that submit to the tribunal's jurisdiction. In effect, all states subject to the underlying legal obligation come to be subject to the soft-law impact of the tribunal, regardless of whether they have formally submitted to the tribunal's jurisdiction. In sum, the decisions of international tribunals create a form of nonbinding, yet influential, international common law. This argument is perhaps counterintuitive. Generally, a tribunal's decisions are thought to be either legally binding or not. But even when a ruling is binding, its impact is quite circumscribed. The decisions of the UN Human Rights Committee ("Committee"), for example, do not carry the force of law at all even with respect to the dispute at issue. The decisions of the International Court of Justice ("ICJ"), on the other hand, are considered binding on the parties to the dispute. The ICJ ruling, however, is binding only on the parties before it and only with respect to the particular case at issue.6 In other words, there is no rule of stare decisis at the ICJ. Thus, while a ruling from the ICJ represents a legally binding resolution of the dispute, it carries the force of law in only a very narrow sense. Of course, the fact that a tribunal's rulings are binding only on the parties before it does not mean that those rulings have no influence on other states' legal expectations. There is no doubt that international tribunals' decisions signal the direction of future rulings and, de facto, define the contours of the legal obligations states face. In the absence of stare decisis these rulings can only be described as a form of soft law.7 That is, they do not formally determine the content of a binding legal obligation. Instead, they are nonbinding interpretations of hard legal obligations. As such, they shape states' expectations and implicate states' reputations for compliance with international law, and so can constrain states' behavior. Using soft law in this way allows states to avoid the normal requirement of state consent. Most obviously, a tribunal's ruling influences other states that may find themselves before that tribunal. Each ruling provides information about how the tribunal is likely to rule in the future, and states can adjust their behavior to take that information into account. …