When did the right of intervention for humanitarian reasons become a frequent justification for state practice in international relations?

The United Nations began the development of universal human rights standards at their outset. However, it wasn’t until after WWII that concern for human rights increased dramatically. The prosecution of Nazi leaders marked the beginning of the modern period of international protection of human rights.

The Conference on Security and Cooperation in Europe met in Helsinki on July 3, 1973, the final outcome of that convention set forth new expectations about human rights behavior. Also, it began the monitoring of human rights policy. Since this time, international implementation procedures have been in continual development. The procedures may include provisions for reporting complaints and violations, judicial decision, the establishment of investigatory committees, and processes for mediation and conciliation.

Recently, the states duty to punish violations has been explicitly addressed in the drafting of treaties, and is increasingly being incorporated into the interpretation of already existing treaties.