Rule of law was helped by social stratification?

This post puzzled me. I quote:

Francis Fukuyama in his recent book "The Origins of Political Order" makes a similar claim about the origination of the rule of law, and so says that India has actually long had it because Brahmins held the state accountable to a set of laws that the king did not create.  However, he finds that India never developed a strong state (like the Chinese did, who on the other hand, never had the social stratification necessary to create the rule of law).

Bears thinking about, caste or social stratification as it is now known created the rule of law? Hmmmm, social law perhaps but that never stopped the damn rulers to do what they wished. I am really not sure that the Brahmins had that power to overrule or manage the rulers. Nothing that I have read says so. The Dharmashastras are full of this stuff but rarely does a ruler actually behave like what it says. And how does that square with the Mughal Empire and its Sharia law?