I believe that depends on the state you live in. Regardless of the law, I believe it's better for the parent to expose the alcohol in a safe way so the temptation to party it up in High School and College is reduced.
When I was a senior in high school my town enacted an ordinance which tried to cut down on teen drinking by enforcing an automatic fine on the drinker and substantial fines on the owner of the property they were drinking on.
That year's party after Jr. Prom was held at a parent's house. The parents were home because they wanted to supervise, and they insisted that anyone who wanted to drink would have to sleep over. We all had to put our keys in a basket.
The police raided the house, found the key basket, and traded citations for keys. They ended up handing out over 100. The parents, who had the fortitude to attempt to house and supervise 100+ drunken high schoolers received massive fines and criminal charges.
Now you might be saying, "well, the law's the law. They got what was coming to them." I can't really argue that. What I can do is point out the consequences:
1. Teens continued to drink (as they will always do);
2. Parents refused to supervise any more of this drinking;
3. Teens refused to put keys in a basket.
So, the results of the ordinance were completely unsupervised teen drinking and increased drunk driving.... Kinda a phyrric victory for the cops and town council if you ask me...