In message 20010730144746.89961.qmail@web12207.mail.yahoo.com, Stephen Date stephend999@yahoo.co.uk writes
I always assumed that the slave buyers were from non-Federation worlds as slavery is legal in the Federation, so the slavers may not have heard of Servalan.
While state-sponsored slavery is legal, I don't think there's any indication that privately owned slaves are. The examples we hear about seem to be the property of the military or commercial organisations.