Kenka Ryoseibai (喧嘩両成敗)
Kenka Ryoseibai was one of the principles of law (jurisprudence) in Medieval Japan. The principle provides that both parties which resorted to violence in a conflict should be equally punished regardless of the right or wrong of the matter.
In the late medieval period, as the nation became unsettled, kosen bosen (offensive and defensive war) broke out frequently to resolve disputes over the boundaries of territories or the like by force (self-help) instead of by bringing them into court. Its intention was to resolve the disputes militarily and briefly to cope with the circumstances. That announced in 1456 was considered the earliest example. Its idea was also introduced into bunkokuho (the law individual sengoku-daimyo [Japanese territorial lord in the Sengoku period] enforced in their own domain) in the Sengoku period (period of warring states) (Japan): Imagawa Kana Mokuroku (Kana List of Articles of the Imagawa) of the Imagawa clan laid down that 'those who engaged in an armed conflict were both to be executed, irrespective of the question of right or wrong,' and 'who having borne and controlled himself under the provocation... and peacefully settled the matter for the moment was judged as reasonable..., and was to be exempt from punishment' (Article 8).
Koshu Hatto no Shidai (the Laws of the Province of Kai) of the Takeda clan laid down that 'both parties to a quarrel leading to violence were to be executed regardless of their reasons; however, those who were involved in quarrels, but who kept their patience were not to be punished.'
This tide remained as the common law up to the early part of the Edo period; and when the government changed its policy to bunjiseiji (civil government), it was criticized by Confucians. Nevertheless, since the idea of Kenka Ryoseibai was simple to understand and convincing for both parties of a quarrel, it was considered that the idea was passed down up to now through the minds of Japanese people. Today, the idea is often quoted by teachers and parents when intervening in children's conflicts.