The global energy sector is in flux, transitioning from reliance on fossil fuels to clean energy sources at an unprecedented pace. This book explores the complex interplay between this transition and international investment law. The book navigates the tension between attracting crucial and expensive investments in clean energy and protecting a state’s right to regulate its energy sector for environmental and other reasons. It analyses how international treaties and investment arbitration tribunals are evolving to address these challenges, examining how the scope of investment protection is being redefined and the delicate balance between stability and regulatory flexibility is being recalibrated. The book delves into this complex landscape, exploring how established legal frameworks, especially international investment law, grapple with the unique characteristics of renewable energy, critical minerals, and rapidly evolving technologies. While offering a roadmap for the current energy transition, the book also identifies unanswered questions. It paves the way for further discussion on critical mineral supply chains and the future of international investment law in a transformed energy landscape.