Pax Romana was Pax Romana because everyone who wasn't peaceful was killed. That's peaceful relative to rome though. So that's this society. This society is like rome.There There is no crime because everyone who commits the slightest infraction or even thinks about it is quickly and quietly removed from the rest of society and killed. The people who are left love the police. Government propagada takes care of the rest.
Another thing you could do is to make the people believe the police are demigods,or maybe agents of God. The police could be led by some one thought to be a god. Bring religion into it. It has been done before.