Rules of Engagement, or RoE, is the preferred method of combat for trueborn Clan Warriors. Trueborn are the product of the eugenics system of the Clans. They are created artificially in laboratories, and genetically engineered to produce the ultimate Warrior. In contrast, freeborn are people who have been given birth the natural way. According to the way of the Clans, only the trueborn are superior and pure. They, by birth right, are with honor, and righteous. Among the elaborate and mysterious ways of the trueborn Warrior is the Rules of Engagement.

RoE was a method of combat devised after the Exodus from Terra, to minimize huge losses of valuable equipment and human lives in combats and battles. The most important aspect of RoE is single opponent combats. The brief general rules of RoE are as follows, and pertains only to BattleMechs vs. BattleMech battles:

• A Warrior will never fire on a 'Mech already engaged with another opponent. This means that no double teaming or gang-banging allowed.
• A Warrior will at no time initiate physical attack, such as charging, punching, kicking, or clubbing.
• Only in the event that a Warrior has no more weapons at his or her disposal, may he or she engage in physical attacks.

Following these basic guidelines ensure that a Clan Warrior will fight with honor. There are other conditions to RoE, that individual Clans will follow. For example, depending on the Clan, a Warrior may or may not be able to:

• Fire on a retreating 'Mech
• Fire on a shutdown or fallen 'Mech
• Fire at the rear of a 'Mech
• Target the head of a 'Mech

Failure to adhere to RoE during combat will cause loss of honor for a Warrior, as well as serious repercussions from his or her commanding officer. The use of IDF, or indirect fire, will also result in a loss of honor.

However, in the event that the enemy fails to follow RoE, one may return the dishonor. For example, if the enemy attacks using physicals, the Warrior may return the physical only to that enemy. In the event where the enemy as a whole act dishonorably, the commanding Clan officer may call a Grand Melee, at which point the battle field becomes a free for all--a Warrior may at this point use any means at his or her disposal to terminate the enemy.