Citizens could sell themselves (and fathers could sell their whole families) into slavery. In some ways it was a form of bankruptcy law. You got paid money for the transaction which you then used to pay off your biggest creditor and you were now under the protection of whomever bought you, from the other creditors. It was illegal to try to force a debt collection from a slave. They had to try and get it from the patron (owner), who had his own little private army of kneecap breakers. Slaves actually had states rights whereas the citizen could simply go whenever, and were left to their own devices, wherever. Slaves also had an "old slaves' home". At the age of 70 any slave could go there and live (something along the lines of the YMCA with food stand). There were times when so many people were selling themselves into slavery for tax reasons and to avoid the draft that the empire (I don't ermember which emperor) started to allow slaves to enlist.
