Well, yes. There are plenty of takes on this. The "Traveller" RPG has a nice one: distributed feudal confederation. There's a nominal emperor, but it's hugely important that he never do almost anything, because "his" empire is a lifetime across.

Nearly the only law is that you don't impede the mail system, and that you pay a small tax to support the fleet that will hammer you into the ground if you impede the mail.