> Dean Ball made this exact point on the Ezra Klein show a few days ago. I always thought laws would get more just with perfect enforcement -- the people passing mandatory sentencing laws for minor drug offenses would think twice if their own children, and not just minorities and unfavourable groups, were subject to the same consequences (instead of rehab or community service).

The problem with perfect enforcement is it requires the same kind of forethought as waterfall development. You rigidly design the specification (law) at the start, then persist with it without deviation from the original plan (at least for a long time). In your example, the lawmakers may still pass the law because they don't think of their kids as drug users, and are distracted by some outrage in some other area.