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Rules of engagement (ROE) are the internal rules or directives among military forces (including individuals) that define the circumstances, conditions, degree, and manner in which the use of force, or actions which might be construed as provocative, may be applied. They provide authorization for and/or limits on, among other things, the use of force and the employment of certain specific capabilities. In some nations, ROE has the status of guidance to military forces, while in other nations, ROE is lawful commands. Rules of engagement do not normally dictate how a result is to be achieved, but will indicate what measures may be unacceptable.
While ROE is used in both domestic and international operations by some militaries, ROE is not used for domestic operations in the United States. Instead, the use of force by the U.S. military in such situations is governed by Rules for the Use of Force (RUF).
An abbreviated description of the rules of engagement may be issued to all personnel. Commonly referred to as a "ROE card", this document provides the soldier with a summary of the ROE regulating the use of force for a particular mission..
While many countries have their own rules of engagement documents, many others do not. There are two primary international rules of engagement manuals that are internationally available: NATO ROE Manual MC 362-1 (restricted to NATO and Partnership for Peace countries); and the San Remo Rules of Engagement Handbook, which is freely available to all on the International Institute of Humanitarian Law (IIHL) website. Created for the IIHL by Commander Alan Cole, Major Phillip Drew, Captain Rob McLaughlin and Professor Dennis Mandsager, the San Remo ROE Handbook has been translated from its English original into French, Chinese, Arabic, Spanish, Hungarian, Russian, Bosnian, and Thai and several other languages. Several countries have used the San Remo handbook as a model for creating their own ROE systems.
The International Institute of Humanitarian Law in San Remo, Italy conducts rules of engagement training course at least once per year, usually in September. Taught by some of the world's foremost authorities on ROE, the course attracts students from around the globe. Similar training by the San Remo ROE drafting team is conducted for the United Nations, staff colleges and other organizations as requested.
All rules of engagement created for use in armed conflict and in the jus ad bellum must comply with international law, as well as the domestic law of the state(s) using them. Any ROE that purport to permit violations of applicable law are void ab initio. Thus, for example, any ROE that would permit the torture of a person would be unlawful. Hence, compendia in ROE Handbooks, such as the San Remo Handbook, only provide ROE options that can comply with international law. Often, violations of the laws of armed conflict are confused with violations of rules of engagement. Insofar as ROE generally regulate the amount or type of force that can be used in a given circumstance, ROE violations are typically related to the use of excessive or unauthorized force or actions. Violations of the laws of armed conflict, on the other hand, consist of violations of the treaties and customary law that make up the laws of armed conflict.
ROE can not be used to negate an individual's right to defend oneself from an attack. If, in peacetime, an individual uses force in self defence, or in the defence of others, then attention must be turned to whether or not that force was reasonable and necessary in the circumstances.