Despite its unbroken attractiveness, the international investment law regime has recently come under pressure to abandon its pre-occupation with investors’ rights and to focus more strongly on sustainable development concerns. This Chapter critically reviews how arbitral jurisprudence has or has not reconciled sustainable development concerns with investment protection. Proceeding from the observation that most international investment agreements ought to be interpreted in accordance with articles 31–33 of the Vienna Convention on the Law of Treaties (VCLT), it argues that it is neither necessary nor sufficient to change the substance of international investment law; instead, non-commercial concerns and state regulatory interests could more convincingly be reconciled with investment protection if arbitral tribunals faithfully and openly employed the applicable rules of treaty interpretation.