In this experience paper, we present the lessons learned from the First University of St. Gallen Grand Challenge 2023, a competition involving interdisciplinary teams tasked with assessing the legal compliance of real-world AI-based systems with the European Union’s Artificial Intelligence Act (AI Act). The AI Act is the very first attempt in the world to regulate AI systems and its potential impact is huge. The competition provided firsthand experience and practical knowledge regarding the AI Act’s requirements. It also highlighted challenges and opportunities for the software engineering and AI communities.CCS CONCEPTS• Social and professional topics → Governmental regulations; • Computing methodologies → Artificial intelligence; • Security and privacy → Privacy protections; • Software and its engineering → Software creation and management.