If you do a bad thing, you get sent to prison. But if you do a good thing, you might get a thank you if you're lucky. But usually you get nought. This seems to be an obvious omission in our legal systems.
So, I suggest, for example, if a person gets sent to prison under the three strikes and you're out law, once they have done three good things in prison, they are let out again. Of course, there would have to be equivalence between the good and the bad, which may mean murderers and heads of multi-nationals don't ever get out. But, I'm sure, with help, people in for theft or minor violence etc. could come up with imaginative ways to balance their account.