The real problem, I think, is when fairness conflicts with effectiveness. If the idea is to do the best by each individual then I guess you’ll want to select the punishment which works best at improving the behaviour of that individual (if you can). But there’s no guarantee that the same punishment will work for everyone. For instance, someone who’s a bit of a tearaway because of difficult home circumstances might benefit massively from a little TLC, whereas someone from a stable home who behaves in the same way on a whim might best be returned to the straight and narrow by a short sharp shock. Effective — yes. But fair? Well, you tell me.