Should the subject of slavery be a bigger deal than it actually is in the setting? Like, if Arabasta or Water 7 are ostensibly obedient to the World Government would they have to tolerate slave merchants from the CDs?
in theory, only a very limited population can be slaves, as seen by the bidding list at Sabaody
So in theory, places like Alabasta and Water 7 could use the slave trade to get rid of their criminals, but ostensibly it’s a practice that’s illegal and most places don’t know that it still exists. Not even the more worldly Straw Hats who keep up with the news knew about it until they actually got to Sabaody (except maybe Robin, and even then it’s not clear). Presumably any leaders who frequent Mariejois for the Reverie would know, but that only has 50 seats and there are more than 250 nations in the WG. Despite how many slaves the Celestial Dragons kill, they’re really only supplying labor for 19 families and one island. Other rich people were seen at the auction house at Sabaody, but you’d have to guess that’s severely limited by the hazardous travel of the Grand Line. The use of slaves just isn’t a thing we see much outside the 1% of the 1% richest people in the world.
The trick the WG uses to circumvent its own laws is to manufacture criminals to provide slave labor. This is really easy for them to do when the biggest court system in the world on Enies Lobby is a kangaroo court where a person is presumed guilty just by being sent to the island. Most get funneled to Impel Down, but I’m sure the Celestial Dragons get their fair share, too.
