It is an interesting idea, but I think there'll be a lot of tweaking to be done to the process to get something effective. For example, how long should the expiration date be, 6 years is to short because of the political football problem, 20 years is long if the laws aren't retroactive. Also what to do with the existing laws? Stage out their expiration? How do we choose which one will expire first? or should there be an easy way to strike down old laws?
"No Bill of Attainder or ex post facto Law shall be passed."
http://www.usconstitution.net/glossary.html#EXPOST
"ex post facto adj. Formulated, enacted, or operating retroactively."
This is, however, a limit on Congress.
Of course, if they harm people, those people can still file civil suits.
And, it would be quite surprising if the "whole new kind of evil" managed to harm people without falling into a category already prohibited by law (i.e., assault).
But, the point remains: you can't be charged for breaking a law that didn't exist at the time you broke it.
No, you can't outlaw The Sims retroactively.
Frankly, I didn't completely follow derefr's post .. Did he really suggest that there could be a need for laws to govern what happens to simulated minds?
And by the way, if you're somehow successful in removing my mind from my body and torturing it in a computer, current laws would apply just fine.
Artificial intelligences with distinct personalities are not here yet, but I see no fundamental bounds to their creation and am pretty optimistic about the timeframe. The question of whether such intelligences qualify as people will become a pressing one at that time, even if it seems abstract to you now.
The idea that we need a separate law for every conceivable circumstance in which a kind of crime could be committed seems weird to me. Torturing people is already widely illegal; the kind of people need not be specified in law.
And it would create havoc in the courts. Recall that the Icelanders settled most of their disputes via blood feuds and something like weregeld. Doing that in the modern age would result in many arguments about retroactive punishment and/or restitution for people convicted under expired laws. you might be found guilty, punished, declared innocent, compensated, and then declared guilty after all and owing the money back.