Like every parent, I will never forget the day we brought our daughter home for the first time. It was an unseasonably warm spring day and, after dumping the luggage from our weeks abroad, we headed straight for the yard. As I set our 17-month-old in the grass, I felt a momentary a rush of relief...

Preemption policies prohibit local governments from passing laws or ordnances that are more robust than what exists at a higher level. For example, a preemption policy could prohibit a city council from passing a soda tax because one doesn't exist at the state level, or a borough council from...