This mock trial selected the case of AURUM ENERGY PARTNERS S.A. v. the Republic of Vardovia for Arbitration Abroad, focusing on the core conflict between international investment protection and the state’s regulatory authority over climate transformation. It is a cutting-edge example of the intersection of investment law and climate law. Kesmark Aurum Corporation invested $1.1 billion in building a green hydrogen project in Vardovia, securing a 25-year concession agreement, stabilization clauses, and policy incentives such as tax and electricity pricing advantages. However, the new government of Vardovia, citing energy sovereignty and the need to comply with the Paris Agreement, enacted legislation to nationalize the green hydrogen industry, unilaterally terminating the agreement, revoking the incentives, and acquiring the project for only $480 million (with an estimated value of $2.4 billion for Aurum). Aurum claimed that the confiscation was illegal and violated principles of fair and equitable treatment, while Vardovia defended itself based on climate public interests and state regulatory authority. The case covers key topics in investment law and intertwines with cutting-edge issues such as climate law and the interpretation of international treaties, aligning with the trends of energy transition and providing opportunities to hone skills in legal analysis, English debate, and document writing.