Much of the text below was copied by me from a letter I wrote to Poul Anderson on Thursday, November 9, 1988. With some slight revisions to make them read more like an essay rather than a letter.
One convict was sentenced to life enslavement after committing murder. As she said to another character (also in Chapter II of A KNIGHT OF GHOSTS AND SHADOWS): "What else would you do with the wicked? Kill them, even for tiny things? Give them costly psychocorrection? Lock them away at public expense, useless to themselves and everybody else? No, let them work. Let the Imperium get some money from selling them the first time, if it can." Treason is also mentioned as carrying the penalty of life enslavement (death was also used to punish treason).
In Chapter IV of ENSIGN FLANDRY, some infractions of military discipline are punished with a device called the "nerve lash." Forty-two years later, in Chapter XIV of A STONE IN HEAVEN, some rebels who voluntarily surrendered to the Imperial authorities are chastised with nothing worse than a "...bit of nerve lash." This means that the Empire's criminal code (both civil and military) ruled that some categories of offenses were most appropriately corrected with corporal punishment.
To sum up, for its human subjects, the Empire used both varying terms of enslavement and corporal punishment to control crime. Obviously, such a system would have to be adjusted to fit the wildly divergent natures and laws of thousands of non-human races in the Empire. Crimes committed by a member of one race against another might be punished by the penalties set by the victim's species. Or limited enslavement and corporal punishment could be used when appropriate. Imperial law also laid down guiding principles, precedents and uniform penalties for such crimes as murder binding on the Empire as a whole. This would be to prevent, say, a Cynthian court from judging, perhaps, a Wodenite too capriciously.
Although many in our Western society would condemn the Empire's penal system (for using slavery and corporal punishment), I cannot when considering the failures of the U.S.'s own criminal justice system. Our reliance on prisons, fines, and "rehabilitation" has not worked. They do not work because many criminals are bad people who like committing crimes. A good argument can be made that all you can do with such felons is punish them and get some recompensational use out of them or remove them from society. Many of our jurists and penologists are infected with the Pelagian delusion of man willing himself to sinless perfection.
So the slave girl we see at the Crystal Moon described in WE CLAIM THESE STARS need not, strictly, be thought to have endured an unusually harsh fate by the standards of her time and society. Most likely, she was convicted of a crime carrying only a limited term of enslavement and the Merseians, being bound to obey the laws of the Empire in such cases, would release her at the end of her term. Unless, of course, she had been convicted of a crime punished by either life enslavement or the death penalty.
I now offer some of Poul Anderson's thoughts on what I wrote above. As he said in his reply letter dated November 19, 1988, "Actually, although the idea of enslavement as punishment for crime was originally something I threw in mention of to add some "local color," its fuller development in later stories about the Terran Empire resulted, paradoxically, from exploring certain possible consequences of libertarianism."
Anderson went on to say libertarians hate the idea of compulsion and would prefer to make contract the basis of all social interaction. Next, he declared that this was only an ideal which could be at best approximated. A libertarian society would minimize or abolish prisons, including attempts at "rehabilitation." Instead, it would focus on restitution. A man convicted of theft, for example, would have to return the stolen property or its equal value, plus paying damages, etc.
To again quote Anderson: "But, to take a single, perhaps melodramatic example--though, alas, not unrealistic--suppose a man has raped a woman. Probably he can't pay adequate money damages, not that there's likely to be that much money in the world anyway. Should he then work for her, unpaid? It seems unlikely he'd would have skills she could use, e.g., gardening, and still more unlikely that she would want him around. So, there is this contract he's signed, to work for her. She can sell the contract to somebody else who does have a use for this character--or who is a broker. Thus libertarianism could result in a revival of chattel slavery!"
Anderson ended by saying this was merely a reductio ad absurdum. But admitted that slavery as a punishment for crime has occasionally occurred in real history. Finally, he stated he was against such an idea but that many things had come to pass he would oppose.
In conclusion, the irony was that the slavery we see in the Terran Empire most likely had its origins during the libertarian era of the Solar Commonwealth and the Polesotechnic League!