Investment treaty arbitration has been criticized in the academic literature for undermining states’ regulatory capacity and for being an “asymmetric” legal system in which third parties affected by foreign investment are not able to hold investors liable before investment tribunals. The Investment Court System (ICS) introduced in the EU-Canada Comprehensive Economic and Trade Agreement (CETA) and the Multilateral Investment Court (MIC) being currently designed by the United Nations Commission on International Trade Law (UNCITRAL)’s Working Group III are reformed models of investment treaty arbitration. Our contribution argues that the ICS and the MIC may still not preserve the right of states to regulate and fail to provide third parties affected by a foreign investment a legal standing in investment disputes. We argue that those flaws could be mitigated by, first, including investor obligations in the future MIC in the form of Environmental and Social Governance (ESG) clauses, and second, by allowing third parties to bring a claim before the MIC when investors have breached ESG clauses. In doing so, we also provide some possible downsides of our proposal in terms of arbitration efficiency and discuss its limitations from the perspective of public international law.