In September 2024, the Pacific Island States of Vanuatu, Fiji, and Samoa officially submitted a proposal to add a fifth crime - ecocide - to the Statute of the International Criminal Court. The faculty and students of the Promise Institutes in LA and Europe have played a significant role in the lead up to this historic moment.

Executive Director Kate Mackintosh is a leading voice in efforts to have severe and widespread or long-term damage to the environment recognized as an international crime of ecocide.

The Promise Institute Working Group on the use of International Criminal Law to Protect the Environment was established in 2020 on the heels of that year’s annual Promise Institute symposium, and released its first report in February 2020. The group then contributed to the Independent Expert Panel for the Legal Definition of Ecocide, which was convened by the Stop Ecocide Foundation at the request of parliamentarians from Sweden's governing parties. Kate Mackintosh served as deputy co-chair of the expert panel, which was led by Philippe Sands QC and Dior Fall Sow, alongside nine other distinguished jurists from around the world.

By June 2021, the panel had completed its groundbreaking work, proposing a definition of ecocide to be added as a new crime under the Rome Statute of the International Criminal Court. This later became the official definition proposed by Vanuatu, Fiji and Samoa in September 2024.

The Promise Institute Europe is continuing to work to support the adoption of the crime, and its implementation in support of environmental and climate justice.