On Liberty question

Hi!
I thought i'd better post this in OI because the book isn't leftist

Can anybody perhaps enlighten this sentence of On Liberty by Mill, talking about the earliest rulers:

They consisted of a governing One, or a governing tribe or caste, who derived their authority from inheritance or conquest, who, at all events, did not hold it at the pleasure of the governed, and whose supremacy men did not venture, perhaps did not desire, to contest, whatever precautions might be taken against its oppressive exercise.

I don't know what is meant with the part in bold.
I'd be really grateful

What I think it means is that people didn't really think about what system of precautions they could set up to avoid the abuse of power by those of authority.

Well he basically advocates in this text placing limits on governments power to stop them infringing on free speech and other liberties, he's just saying people didn't really consider the ways in which they might do this in the times of autocratic Monarchs who gained their power through bloodline, violence and oppression