This book examines the implementation of international law within the Irish legal system, focusing on public international law as the body of rules binding on states in their interactions. It primarily structures its analysis around the principal sources of international law, as outlined in Article 38(1) of the Statute of the International Court of Justice, while also considering other important elements such as acts of international organizations. The book explores the implementation of treaties, customary international law, acts of international organizations, and international judicial decisions within both the Irish and European Union legal systems. It aims to provide a comprehensive overview of the status and effect of international law in the Irish legal system, situating this examination within the context of Ireland's EU membership. The book concludes with a brief overview of Ireland's main international obligations in specialized areas of practice, highlighting the potential relevance of international law across many fields of law in Ireland.