International investment tribunals are frequently required to interpret and apply rules of Customary International Law (CIL) in investor-State disputes. This article examines how investor-State tribunals, in particular those constituted on the basis of the Energy Charter Treaty (ECT), have interpreted the CIL ‘full reparation’ standard regarding damages and reparation. By reference to ECT jurisprudence it is established that tribunals often utilize teleological interpretive tools to give content to this norm. Furthermore, some critical comments are made concerning the manner in which ECT tribunals subsequently apply the ‘full reparation’ standard. It is argued that the combination of the commonly adopted approaches to interpretation and application may explain why investors are occasionally capable of obtaining significant amounts of compensation in these public law disputes.

国际投资法庭经常需要解释和适用国际习惯法（规则CIL在投资者与国家争端）。本文研究了投资者国家法庭，特别是那些根据《能源宪章条约》（ECT）组成的法庭，如何解释了CIL关于损害赔偿和赔偿的“充分赔偿”标准。参照ECT的判例，可以确定法庭经常利用目的论的解释工具为该规范提供内容。此外，对于ECT的方式也提出了一些批评意见。法庭随后适用“全面赔偿”标准。有人认为，通常采用的解释和适用方法的结合可以解释为什么投资者有时能够在这些公法纠纷中获得可观的赔偿。