Understanding the philosophy of law and justice in relation to international law and humanitarian law is crucial for comprehending the principles and concepts that underpin these legal frameworks. Here are some suggested sources that can aid in gaining a comprehensive understanding of this subject:

1. International Law and the Philosophy of Law:
- "The Philosophy of International Law" by Samantha Besson and John Tasioulas: This book explores the philosophical foundations of international law, addressing key issues such as the sources of international law, the nature of international legal obligation, and the relationship between international law and state sovereignty.

2. Justice in International Law:
- "The Idea of Justice in International Law" by Allen Buchanan: This work delves into the concept of justice in international law, examining different theories and perspectives on the subject. It explores the tension between justice and other principles, such as state interests and order, and analyzes the role of international institutions in promoting justice.

3. Humanitarian Law and Justice:
- "The Oxford Handbook of International Humanitarian Law" edited by Andrew Clapham and Paola Gaeta: This comprehensive handbook covers various aspects of international humanitarian law, including the relationship between humanitarian law and justice. It explores topics such as the prosecution of war crimes, the principle of proportionality, and the protection of civilians during armed conflicts.

- "Humanitarian Law: The Principles of Humanity and Justice in Times of War" by Richard Baxter: This book provides a detailed analysis of the principles of humanity and justice in humanitarian law. It examines the ethical considerations underlying these principles and their application in armed conflicts.

4. International Criminal Law and Justice:
- "International Criminal Law" by Antonio Cassese: This book offers an in-depth exploration of international criminal law, focusing on the prosecution and punishment of individuals for international crimes such as genocide, war crimes, and crimes against humanity. It discusses the principles of justice that underpin international criminal law and the role of international criminal tribunals in upholding these principles.

- "The International Criminal Court and the Philosophy of International Law" by Morten Bergsmo: This work examines the philosophy of international law in the context of the International Criminal Court (ICC). It analyzes the principles of justice and fairness in international criminal proceedings and explores the challenges faced by the ICC in achieving its objectives.

By consulting these sources, you will develop a solid foundation in the philosophy of law and justice in relation to international law and humanitarian law. Remember to critically analyze the content and integrate your understanding with real-world examples to enhance your knowledge in this field.