Not quite...

Medieval kings were considered the embodiment of the government, but that didn't make them autocratic. Indeed, they were not only bound by a thicket of obligations and customs, but authority itself is only legitimate when it is just, a view that is traditional; it is modern legal positivism that roots authority in fiat, making it inherently tyrannical.

> Indeed, they were not only bound by a thicket of obligations and customs, but authority itself is only legitimate when it is just, a view that is traditional;

Ultimately they were bound not by tradition, but by the reality that they may lose their heads, often at the hands of a competing relative, but also at the hands of starving subjects.