>> Sá konungr hefir ráðit fyrir Danmörku, er Hringr hét. Hann var
>> Skjaldarson, Dagssonar.
>>
>> That king who had ruled (over) Denmark was called Hringr
>
> We assumed "has ruled (over)", but Alan has suggested "has authority
> over", ráð + the definite article -it. He could be right, but at the
> moment I'm still inclining towards "has ruled", as the usual saga opening
> formula is the past tense of the verb ráða, thus: réð fyrir. And compare
> the beginning of paragraph two: Sviði hefir karl nefndr verit.

I'm with you here. Interpreting 'ráðit' as a noun here would be quite odd.
- Haukur