Investment treaties protect foreign investors who contract with sovereign states. It remains unclear, however, whether parties are free to contract around these treaty rules, or whether treaty provisions should be understood as mandatory terms that constrain party choice. While investment treaties clearly apply to contracts in some way, they are silent as to how these instruments ultimately interact. Moreover, arbitral jurisprudence has varied wildly on this point, creating significant problems of certainty, efficiency, and fairness – for states and foreign investors alike. This Article reappraises the treaty/contract issue from the ex ante perspective of contracting states and foreign investors. I make three novel claims: one conceptual, one descriptive, and one normative. First, I argue that investment treaties must be understood as having generated a rudimentary, yet broad, law of contracts – governing agreements between states and foreign investors on pivotal issues, from substantive rights and duties, to damages and forum selection. Second, I argue that this emerging international law of contracts has developed sporadically, irregularly, and inconsistently, due in part to a tendency among tribunals to confuse the logics of contract and property. As a result, it remains undecided whether contracting parties should understand background treaty norms as defaults, sticky defaults, or mandatory terms – leaving the meaning of their contracts under a cloud of doubt. Third, I argue that the best way to resolve this problem for both states and investors, ex ante, is generally to privilege their contractual arrangements over background treaty rules. Even when these parties have different interests and values at stake, the treaty/contract problem is not zero-sum. Both sides usually stand to benefit from the freedom to negotiate around treaty rules as mere defaults – though I explore certain cases where treaty norms might justifiably exert a greater pull. In general, prioritizing party choice is not only optimal from the economic standpoint – it also provides states with the tools to secure their future capacities to regulate in the public interest
