If Dwemer law comes from the Altmer, the Dwemer do as well.
Thats something of a stretch.
We know this because Topal the Pilot writes about them in Father of the Niben. Topal was an Aldmer, so this occured before the various schisms that led to Altmer, Chimer and Dwemer.
Yes, but Topal also records orcs. If we take him at his word (and I see no real reason not to) then Orsimer are actually the direct spawn of the Elhnofey, and not of the Aldmer.
This goes against most of what we've ever heard of the orcs. So are we just supposed to treat it as outdated lore? I tend to ignore it for this reason, but it was included in Skyrim, so the devs still think its relevant.