Justices of the High Court of Australia have a broad discretion to follow foreign judicial decisions based on whether they consider a decision to be persuasive. But it is difficult to assess what it is about a foreign decision that makes it likely to be followed by the High Court. This has created uncertainty that is problematic for both litigants and the court. To help address the uncertainty associated with the High Court's use of foreign decisions, this article identifies common factors that explain when the High Court is likely to follow foreign decisions. By drawing on theories of persuasive authority and closely analysing decisions from 2015 and 2016, I argue that the High Court is more likely to follow foreign decisions that: (1) are about legislation or instruments with similar words to those in dispute; (2) emanate from certain jurisdictions; (3) are from apex or appellate courts; (4) are raised by litigants; and (5) reflect values common to the Australian legal system. Conversely, the area of law, international consensus and the date of foreign decisions are unlikely to influence the High Court's willingness to follow foreign decisions. These factors can help litigants use foreign decisions effectively and may be used by legal scholars to scrutinise the legitimacy of the High Court's use of foreign decisions and to address the normative question of how the High Court should use foreign law.

Investment arbitration awards often give the impression that investment treaties are designed to reflect the interests of two actors: “investors” and “states”. There are in fact a myriad of actors, or “voices”, behind each word in an investment agreement. This chapter identifies three broad categories of voices: voices inside, outside and among states. It explores the range of voices that influence investment treaty text by reference to those three categories. The chapter argues that modern investment treaties are multifaceted texts that are influenced by a range of voices from within and outside of government.