Many people believe that the most effective way to reduce teen alcohol abuse is to reduce teen access to alcohol. Surveys of high school students find that the majority of teens who drink obtain their alcohol from adults. Teens may pay adult strangers or friends who are over age twenty-one to buy alcohol for them.

Many parents also provide their teenage children with alcohol, a practice that is legal in all fifty states. But some parents also host parties—often after high school graduation—where alcohol is served, allowing their teenager’s friends to drink as well. In many communities this had led to conflicts among parents, many of whom believe that providing alcohol to teenagers is dangerous and irresponsible.

Some communities and states have responded by passing social host liability laws. Under these laws...