here is what wikipedia has to say about Genghis Khan.
Genghis Khan
Contrary to his ruthless and barbaric reputation in the west, Genghis Khan promulgated several enlightened policies that would not become common practice in Europe for centuries more.
He guaranteed freedom of religion, protecting the rights of Buddhists, Muslims, Christians, and Hindus alike. Genghis Khan himself worshiped the sky, but he forbade the killing of priests, monks, nuns, mullahs, and other holy people.
The Great Khan also protected enemy envoys and ambassadors, no matter what message they brought. Unlike most of the conquered peoples, the Mongols eschewed torture and mutilation of prisoners.
Finally, the khan himself was bound by these laws as well as the common people.