This article argues that State autonomy in setting the level of protection for permissible regulatory aims can be better operationalised in the investment treaty regime. The article draws on comparative insights from WTO law, where it is established that WTO members have the right to determine the level of protection for permissible regulatory aims, although significant disciplines are placed on the means used to achieve those aims. It is then argued that investment treaties are, properly interpreted, consistent with the idea that States retain autonomy to determine the level of protection for permissible regulatory aims. Finally, the article proposes removing from the fair and equitable treatment and indirect expropriation standards proportionality balancing stricto sensu, as this undermines State autonomy in setting the level of protection. Overall, this article argues for a partial reorientation of investment law, in which non-discriminatory measures that pursue a permissible regulatory aim, including at a particular level, should not amount to a breach of a treaty where a State uses the means that involve the least possible restriction of the competing interests protected by relevant investment treaty obligations.

The dyadic rule–exception structure common to many legal systems has posed particular interpretive difficulties in international trade and investment law. Adjudicators have interpreted general and security exceptions in GATT, GATS and cognate provisions of investment treaties in divergent ways, and the analytic character of these provisions is under-theorised in the literature. This article argues that we should understand exceptions from a deontological perspective as permissions that affirm governmental regulatory capacity and thus limit the scope of the commands set out in the treaty. This characterisation of exceptions has both symbolic and practical implications, of which this article discusses two: determining the exception's applicability as a preliminary matter rather than as a defence, which would in turn permit consideration of regulatory purpose at the point of obligation; and whether the applicability of an exception is properly a question of merits or jurisdiction.