A zero-tolerance law means that anyone who violates it is subject to mandatory punishment, regardless of extenuating circumstances. Under zero-tolerance policies, judges or law enforcers cannot exercise discretion in deciding what penalties to slap for infractions.
A zero-tolerance law prohibits alcohol consumption by a student on school property and imposes a mandatory 10-day suspension for noncompliance. Such a law could have the same punishment for a student who uses mouthwash that contains alcohol ahead of a dental appointment, as another who drinks a six-pack of beer within the school premises. In both infractions, the extent and history of alcohol abuse has no bearing on the legal ramifications.
The zero-tolerance policy towards underage drunk driving is in line with prohibition of use of alcohol for anyone under the age of 21. Since anyone under the age of 21 should not drink beer, states enacted laws that made it illegal for such a person to drink just before or while operating a motor vehicle.
Workplace harassment and drug abuse can also be addressed via zero-tolerance laws. The laws also apply in gun control rules at school. However, the efficacy of such policies is subject to question, with arguments being brought against their tendency to be ruthless and excessive.