We join you now on this Editorial Edition of Net-7 News, with your Anchor-rat, the Pakkrat:
My game just came off a sub-plot where the crew of the Ares discovered a mass Low-berth cargo container filled with four female and two male identical Darrian twins, (or were they clones?) smuggled into their cargo hold Armory. Each were found packed in like sardines and wearing a TL 15 circlet with micro-miniature electronics. These circlets erased short- and mid-term memory in the brain but left basic survial skills intact, (e.g. reading, writing, basic math, speech, language, etc).
The three Darrian crew on board the Ares, though detesting such crude modalities could not fathom what the 'sextuplets' were to be used for since none of them, upon reviving, could remember what they were before awakening.
Now, were the sextuplets really twins, cloned females and cloned males of twin Darrians? Were they test subjects? Cloned organ sources? The applications could be endless.
My point is that though we can use 'slavery' as a catch-all term to pluck on the heartstrings of the player-characers, the Far Future can use any number of workarounds for the leagalisation of such unknowns as the above example.
Let us not forget that in some polities, slavery (even if it is upward-mobile, graduating to freeman citizenship), can be legal and even seen as gentle social uplift for those who cannot or will not mesh with whatever world they currently reside. Some polities might see this as a service to better those enslaved for such upward graduation during service. One such polity, to name an example, was the Society of Equals in the fan-made Sourcebook: Gvurrdon Sector, (before Mongoose wrote their more-virginal version).
Another polity, further Coreward in Knoellighz Sector, that I am currently developing features highly valued and carefully treated 'slaves'. Six million TL 15, scientific clones on Dzagok (Knoellighz 2436) serve, somewhat blindly, the 'privateers' from UOSA (Knoellighz 2237) in a clon-ish need to be helpful and solve problems and such. They are being taken advantage of, to be sure, but each clone scientist is given safety, security and is returned to Dzagok when the given project is completed. UOSA Syndicate Privateers do their best - as privateers and as Corsairs - to provide the materials the clone scientists request for each project and the needs of their cloneworld Dzagok. Is this slavery in the Third Imperium's eyes far to Rimward? (For more information, search "Ascendancy Pact" on the wiki.)
Two examples of how slavery can be seen as a social uplift service rather than an atrocity of civilization,
Reporting from Serue (Knoellighz 1221), this is the Pakkrat. :CoW:
P.S. Another society where sophonts might be considered 'enslaved' might be Roethoeegaeaegz (Knoellighz 1726), but that's more sexism due to need for survival. YMMV
T-shirt Hell: "Slavery. Gets Sh*t Done."