This article investigates whether environmental planning law can demonstrate ethical responsibility for its role in settler colonialism. Planning law contributes to settler colonialism by diminishing, excluding, and eliminating alternative views of land that are fundamental to First Nations culture, philosophy, and law/lore. The article adopts a transnational legal frame that recognizes and promotes First Nations as sovereign. The investigation is focused primarily on the planning law system in New South Wales (NSW), Australia, while being guided by interpretations and applications of the rights of First Nations peoples by courts in Canada. It is argued that state planning law in NSW fails to give effect to ethical responsibility because its operation continues to dominate and marginalize Aboriginal legal culture by eroding the necessary ontological and epistemic relationships with land. However, there is potential for change. Opportunities to disrupt settler colonialism have emerged through bottom-up litigation, which has promoted interpretations, applications, and implementation of law that can be performed in ways that resonate with Canadian case law. While the absence of treaty or constitution-based rights protection in NSW and Australia means that the transplant is not seamless, the article argues that laws should not be interpreted and applied in ways that perpetuate settler colonialism where alternative interpretations can lead to a different outcome.