What was the principle of legitimacy?

I believe that legitimacy is as basic human need. Having the right to receive fair and just treatment. Like the need to belong.

The principle of legitimacy was an idea proposed on September of 1814 at the Congress of Vienna that was used as a guideline for rulers in Europe after the fall of Napoleon. Since napoleon was not an absolute monarch other rulers saw him as a threat to the "old order" or the system that made the monarch have all power along with the Catholic church of the time. The principle was basically saying that all lawful monarchs would be restored to full power in order to keep peace and order. But, besides in the restoration of the Bourbon monarchy in France it was largely ignored.