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Customary international humanitarian law: reducing the human cost of armed conflict

09-08-2010 Interview

The rules of customary international humanitarian law (IHL) aim to protect the victims of armed conflict. They complement the protection provided by treaty law and fill certain gaps resulting from treaties not having been ratified. The ICRC's head of project for customary law, Jean-Marie Henckaerts, explains why customary IHL is so important and talks about the launch of a new database to make these essential rules more accessible.

  Jean-Marie Henckaerts    
      Customary IHL database

What is customary international humanitarian law?  

 Customary international humanitarian law is a set of unwritten rules derived from a general, or common, practice which is acknowledged as law. It's the basic standard of conduct in armed conflict accepted by the world community. Customary international humanitarian law is applicable universally – independently of the application of treaty law – and is based on extensive and virtually uniform State practice regarded as law.  

At the request of the international community, the ICRC undertook an extensive study into current State practice in international humanitarian law in order to identify customary law in this area. Before the study was published, the rules were unwritten. Today, the study has contributed to identifying the common core of international humanitarian law binding on all parties to all armed conflicts.  


 There are already many treaties pertaining to armed conflict. Why is customary international humanitarian law important?  

Customary international humanitarian law is important because its rules can reduce the human cost of armed conflict. It complements the protection provided for conflict victims by treaty law, and fills in certain gaps resulting from treaties not having been ratified or from treaty law lacking detailed rules on non-international armed conflict.  

Although the 1949 Geneva Conventions have been universally ratified, for example, other treaties of international humanitarian law, such as the 1977 Additional Protocols, have not. As a result, victims of armed conflict, particularly those affected by non-international armed conflict, are not always fully protected by treaty law. That is why it was necessary to determine which rules are part of customary law and therefore applicable to all parties to a conflict, regardless of their treaty obligations.  

In addition, a large proportion of today's armed conflicts are non-international, and treaty-based international humanitarian law doesn't regulate them in sufficient detail. These conflicts are subject to far fewer treaty rules than are international conflicts. For example, Additional Protocol II, which pertains to non-international armed conflict, contains a mere 15 substantive articles, whereas Additional Protocol I, which pertains to international armed conflict, has more than 80.   

It was important, therefore, to determine whether customary international law regulates non-international armed conflict in more detail than does treaty law. The conclusions of the ICRC study are that the basic rules on the conduct of hostilities, on the use of means and methods of warfare and on the treatment of persons in the hands of a party to a conflict are fully applicable in non-international armed conflicts.  


 How has the customary international humanitarian law study been used since it was published?  

The study has been used in various ways by a whole range of entities. First and foremost, the ICRC has used the study as an important legal reference in international and non-international armed conflicts. The organization refers to it in its dialogue with parties to conflict in order to identify humanitarian rules by which combatants or parties must abide.  

The study has been used by the United Nations, international and mixed criminal courts and tribunals, national courts and non-governmental organizations. For example, on the basis of practice collected by the study, the Special Court for Sierra Leone concluded that the recruitment of child soldiers is a war crime in non-international armed conflicts, thus enhancing the protection for children being recruited and used as child soldiers.  

In addition, the reports of UN Special Rapporteurs on the conflicts in southern Lebanon (2006) and Gaza (2009) relied on the study to identify the customary rules of international humanitarian law applicable in those conflicts.  

In many States customary international law can be invoked before national courts and tribunals. Such was the case for example in Israel, where the Supreme Court delivered a judgment in 2008 concerning restrictions on the flow of fuel and electricity to Gaza. The court referred to customary international humanitarian law and the ICRC study stating that "each party to a conflict is obliged to refrain from disrupting the passage of basic humanitarian relief to populations needing it in areas under its control."  


 Why was the database launched?  

The formation of customary law is a dynamic process. The original study included practice up until 2003. The ICRC and the British Red Cross therefore teamed up to update the practice contained in Volume II of the study. The ICRC recognized the need for the research to be available as a resource for anyone following the developments in the application and interpretation of international humanitarian law and for any future weighing of State practice in the assessment of customary international humanitarian law. The ICRC understood the value of consolidating the material into one source which would be accessible worldwide. The database allows for regular updates and can be easily navigated.  


 What are the advantages of the customary international humanitarian law database and how does it work?  

The advantages of the database, compared to the print version, are its easy, free access and its search functions. In addition to providing the full text of the study, presented per chapter and per rule, the database also allows practitioners and academics to carry out research using three main search parameters: country, type of practice and subject matter. Using the advanced search function, one can thus look up what a particular State has included in its military manuals, legislation and/or case law about any of the topics covered in the study. The use of the database is quite easy and intuitive. We encourage everyone to try it out for themselves  


 What does the ICRC hope to achieve with the new database?  

Ultimately, the ICRC hopes that victims of armed conflict will receive greater legal protection through compliance with customary international humanitarian law. As a first step, therefore, the rules of customary international humanitarian law and the practice underlying them had to be made easily accessible.