Contractualism in the Law of Treaties

When Henry Sumner Maine famously observed that “the movement of the progressive societies has hitherto been a movement from Status to Contract,” he was invoking contract not as a device for binding parties to their commitments but, rather, as a metaphor for freedom. That metaphor lies at the heart of what legal scholars have come to call contractualism (or, sometimes, contractarianism)-the idea that people should be free to decide with whom, for what, and on which terms they enter agreements and that the law should minimize the constraints it places on these decisions. It is a proposition rooted in the values of liberty and efficiency-in the view that parties not only have a right to autonomy in structuring their relationships, but also are usually best situated to know what is good for them. And it has proved influential well beyond the law of contracts. Indeed, notwithstanding the highly anticipated, but ultimately unrealized, “death of contract,” contractualism has been urged on a growing variety of fields, including the law of corporations, bankruptcy, trusts, professional responsibility, family law, and environmental regulation. As Max Weber stressed, however, “in no legal order is freedom of contract unlimited in the sense that the law would place its guaranty of coercion at the disposal of all and every agreement regardless of its terms.” The existence of at least some mandatory rules-rules that may neither be varied nor waived by the parties to an agreement-has been justified by courts, legislatures, and legal scholars as necessary to address three problems inherent in the institution of contract: (1) the possibility that an agreement would have adverse effects on the protected rights of third parties, including those ostensibly represented by one of the parties to the agreement; (2) differences in capacity, knowledge, and power between contracting parties that undermine the voluntariness and fairness of their agreements; and (3) the need to protect the legitimacy and efficiency of the legal system when it is called on to enforce or invalidate an agreement between its subjects. What this Article examines is whether the freedom of contract of sovereign states is similarly constrained.