Civs that have social policies from the freedom tree shouldn't be able to raze cities.
It's a bit odd that the autocracy tree has a social policy (police state) which actually makes razing a city less useful, because police state gives a bonus to occupation happiness. This isn't suppose to reflect real "happiness"; rather it's suppose to reflect the captured population being controlled by a state police force (like the Gestopo or SS).
So the police state country has less reason to raze, which is the opposite of what happened historically.