Defining environmental justice in the context of investment arbitration is a challenge. This question arises primarily in circumstances in which foreign investment has an actual or potential impact on the host state population's health, environment, or socio-cultural values. Under normal circumstances, the right of access to justice should be guaranteed by the law and the justice system of the host state. However, the right of access to justice declines when the controversy is taken to investment arbitration.  While the problem of environmental protection has been addressed in ISDS from the State perspective and its power to regulate, the rights of non-disputing parties and their legitimacy have been relegated. Awards in investment arbitration qualify as environmental decisions. Therefore, more than the traditional approach to Amicus participation in dispute resolution proceedings is needed under the perspective of procedural environmental rights recognised under several international environmental law instruments. This includes the scope of access to the information generated within the arbitration procedure, which should be available proactively and the possibility of remedies when there is a breach of environmental obligations of the investor who brings up its claim in the Investor-State Dispute Settlement system. To address this issue, developing a new model that considers environmental justice as part of investment arbitration is needed to achieve greater consistency and procedural certainty while safeguarding access to environmental justice.