This book explores the scope and the limits of what is appropriate for regional action in the maintenance of peace and security. It offers a comparative study of legal regulation of the use of force in the mechanisms for the maintenance of peace and security of different security regions in the context of the UN system and general international law. The book compares the written law and the actual practice of organizations to gain a better comprehension of how the regional organizations interpret and apply international law, especially, what regards the use of force.