I think this is a ruling that's hard to justify. There are many frameworks under which the judge could have chosen to rule, it could be treated as assault, or some type of aggravated assault/battery, if the lead can be measured in the people who consumed it, it could be treated as fraud, since the water is presumably sold, etc. and reasoning about that it would ordinarily be a punishable tort would make it clear that the government can't impose that sort of thing either, just as it can't send anyone out to punch people.