The article addresses the relationship between judicial autonomy and the autonomy of the parties principles. The issue is not addressed so much through the lens of the procedural rules on the conduct of the proceedings, as through the prism of the general principles of adjudication which dictate the boundaries of judicial, or arbitral, decision-making. The focus will be on the combination between the principles ne, ultra and infra, petita and non liquet as they flow from the consensual nature of international adjudication and arbitration, on the one hand, and the principle jura novit curia which mirrors the autonomy of the judicial function, on the other. The analysis does not draw from national legal systems, nor from commercial arbitration. Due to the significantly different configuration of the principles at issue in different jurisdictions, it will focus on international litigation as an autonomous phenomenon. It will address firstly inter-state adjudication and then international investment arbitration. Special attention will be given to the ICSID system in consideration of its unique annulment mechanism. The article draws from researched case law an encouragement, if not simply the need, for international adjudicative bodies to undertake a proactive attitude in the conduct of the proceedings. More generally potentials emerge from the analysis, to the effect that not only inter-state adjudication may impact on investor-state arbitration, but also vice versa.