Amata LireinA bit of both. Imperial law forbids the trade of Imperial slaves outside Imperial space. And in most of the rest of the bubble slavery in any form is illegal, even if it's voluntary indentured servitude (what Imperial slavery really is).
Gotcha, I figured the external laws were there, but the imperial law also makes sense as it would put the imperial slave outside the system which they originally consented to serve in, which would cause them to lose their social securities.