Rule 140. The obligation to respect and ensure respect for international humanitarian law does not depend on reciprocity.
Volume II, Chapter 40, Section B.
State practice establishes this rule as a norm of customary international law applicable in both international and non-international armed conflicts. This rule must be distinguished from the concept of reprisals, which is addressed in Chapter 41.
The Geneva Conventions emphasize in common Article 1 that the High Contracting Parties undertake to respect and ensure respect for the Conventions “in all circumstances”.
The rules in common Article 3 must also be observed “in all circumstances”.
General recognition that respect for treaties of a “humanitarian nature” cannot be dependent on respect by other States parties is found in the Vienna Convention on the Law of Treaties.
The rule that international humanitarian law must be respected even if the adversary does not do so is set forth in many military manuals, some of which are applicable in non-international armed conflicts.
Some military manuals explain that the practical utility of respecting the law is that it encourages respect by the adversary, but they do not thereby imply that respect is subject to reciprocity.
The Special Court of Cassation in the Netherlands in the Rauter case
in 1948 and the US Military Tribunal at Nuremberg in the Von Leeb (The High Command Trial) case
in 1947–1948 rejected the argument by the defendants that they were released from their obligation to respect international humanitarian law because the adversary had violated it.
This rule is also supported by official statements.
The International Court of Justice, in the Namibia case
in 1971, and the International Criminal Tribunal for the former Yugoslavia, in its review of the indictment in the Martić case
in 1996 and in its judgment in the Kupreškić case
in 2000, stated that it was a general principle of law that legal obligations of a humanitarian nature could not be dependent on reciprocity.
These statements and the context in which they were made make it clear that this principle is valid for any obligation of a humanitarian nature, whether in international or non-international armed conflicts.