The essay critiques prevailing descriptions of investor-state arbitration (ISDS) that see this mechanism as a form of ‘public’ adjudication requiring exclusively ‘public law’ reforms going forward, culminating in, as the European Union has recently suggested in the course of negotiations for the investment chapter of the Trans-Atlantic Partnership, its replacement by a permanent international investment court in lieu of arbitration using party-appointed arbitrators. It is skeptical of the ostensible public/private divide and most of the ten reasons advanced in the literature, premised on that divide, for concluding that the international investment regime, and particularly ISDS, is public. It next critiques ten widely praised public law prescriptions for change to the regime or ISDS. It concludes with ten broad lessons for why ISDS, in its current form, is best viewed as a ‘hybrid’ between public and private.