The ICSID annulment mechanism is coming under ever greater criticism from practitioners, parties, and academics alike. This criticism has become more pronounced after the CMS v. Argentina1 annulment decision. The CMS decision again has sparked talk of broader systemic reform to the ICSID, with commentators raising legitimacy concerns about the awards rendered by the institution. This article seeks to analyze, in light of recent annulment decisions, the systemic problem these criticisms have brought to the fore in the annulment mechanism. Having identified the problem, it will then discuss the prevalent solution of introducing a formal ICSID appeals structure. Next, it will discuss a more external approach: the codification of international investment law and the opportunities and challenges it would provide. It will conclude not with a ready-made answer, or manifesto for change, but rather with an appeal to seek a solution that combines the advantages of an appeals structure with those of an investment law edict or restatement.