The UN Charter and the Vienna Convention on the Law of Treaties require interpreting treaties and settling international disputes in conformity with the principles of justice and international law. This contribution discusses procedural and substantive principles of justice which the international judge may take into account in interpreting international economic agreements. The sovereign equality of states underlying the international law of coexistence as well as the international law of intergovernmental cooperation must be interpreted in conformity with the universal recognition of human dignity as a source of inalienable human rights. The universal recognition of economic and social human rights further requires taking into account solidarity principles, as proposed also by the sociological approach to international law. The constitutional structures and citizen-oriented functions of the law of international economic organizations liberalizing and regulating mutually beneficial market transactions among citizens require judges to engage in a careful balancing of state-centered and citizen-oriented principles of international law, including respect for the emerging human right to democratic decision-making. This modern international integration law and the increasing number of international constitutional rules promote the reconciliation of the various state-centered approaches, human rights approaches, sociological approaches and policy-approaches to international law as a system not only of international rules and legal pluralism but also of constitutionally limited decision-making processes and struggles for human rights.