The origin and historical evolution of the law relating to local remedies provides an interesting instance of how some modern rules of international law came into existence and took their present form. The requirement that local remedies should be resorted to seems to have been recognized in the early history of Europe, before the modern national state had been born, in the relations between sovereign territories or individual communities, in regard to the granting of authority to take reprisals. It is to the ancient practice of reprisals that the historical roots of the modern rule of local remedies is apparently to be traced. While even in primitive societies there is evidence that reprisals as an expression of self-help and of communal solidarity were carried out without the imposition of restrictions, later they became associated with the notion that aliens were entitled to have justice done to them when they had been wronged. Reprisals consequently came to be permitted when an alien had suffered a denial of justice as a condition precedent. Reprisals could no longer be regarded as purely private acts of revenge. They were taken and became lawful only provided they were authorized by the sovereign of the injured alien and only when there was a failure on the part of the sovereign of the wrongdoer to accord justice to the alien. Public authority thus became involved to the extent that it authorized and limited private acts of revenge.