Laws with retrospective effect?
No, it's okay, they're really bad people (trust me, they will be. You can trust me, right?), and even though keeping people locked up after they've done their time is anathematic to the whole rule of law thing, I'm sure you'll agree that the rule of law is seriously overrated. How does it help businesses export their products? How much tax does it pay? Will it shave anything off our government's debt levels?
The rule of law needs to get a job, get a decent haircut, and knuckle down. The world doesn't owe it a living. And look at the people it's been hanging around with.
If the rule of law isn't even prepared to pay its own way, why should we pay any attention to it?