From what Krem tells us, it does seems that those who sign themselves into contractual slavery like his father are better protected and more taken care of than non-citizen, privately-owned slaves, which would imply that some kind of regulation might exist in place to prevent any abuses?
After all, we see that reneging on a contract in Antiva and Orlais is seen as uncivilised to the point of anathema amongst the nobility, so it's likely that Tevinter too has similar penalties in place to prevent Magisters from going around killing these temporary wards of the state?
What I want to know is the rules and distinctions that the rest of Thedas have about this kind of thing, since from DA2, it's (apparently) legal for someone in Kirkwall to sell themselves into indentured servitude, meaning that Hawke and their siblings were at one point no different from Krem's father?
That's what I am thinking. Dorian is of the opnion that if ever a citizen falls into hard times they can apply for some sort of indentured servitude and are then "property of Tevinter" or whatever fancy word they use. This is a good thing (in his eyes) becuase then rather than never find a job and remaining poor, that person can then put their skills to use, while their family benefits.
Then there's Krems dad who did just that. In the end, though, these people have useful skills.
I doubt that people being kidnapped from other countries have any rights. If anything they are "black market" slaves. Not sanctioned by the Tevinter gov't on paper