The Legitimacy of Arbitral Reasoning: On Authority and Authorisation in International Investment Dispute Settlement

The institution of investment treaty arbitration fundamentally questions traditional correlations between legitimation procedures and legitimate authority, as well as between individual, case-to case arbitration and arbitration as a highly effective international adjudicative system. It oscillates between contractual autonomy in proceedings and traits of substantive public law with regards to grounds for and merits of claims. By engaging with an emerging scholarship on procedural and ethical determinants of investor-state dispute settlement, this article explores and argues for a scholarly sensitivity towards a structural co-originality of procedural authorisation and arbitral authority. Demonstrating that responsibility and accountability are decisive and still under-theorised procedural factors relating to legitimation and legitimacy perceptions, the article concludes with a normative account of the nature of legal reasoning in investment treaty arbitration. Accentuating the intrinsic correlation of internal to external, and autonomous to instrumental procedural objectives in the craftsmanship of writing arbitral awards adds meaningfully to what has been labelled a ‘jurisprudence constante’ and thus identified as legitimate corpus of arbitral decisions.