Despite Morrowind being a part of the empire, they still retain many of their traditions and values. Slavery used to be extremely common in Morrowind, and slaves were most either of Khajiit or Argonians. There are anti-slaver groups who do help smuggles slaves out of Morrowind and back to their homelands. Despite the Empire looking down on slavery, they are unable to openly intervene in the laws of other lands in the empire.