Mark Kleiman, as usual, does a great job summarizing the drinking age quandary:
Setting the minimum legal drinking age at 21 saves lives by reducing drunk driving, and not just among the 18-to-21’s; if 18-year-old high school seniors can buy beer at the supermarket, then 16-year-old high school sophomores have access to it. Common sense and evidence agree: drinking and driving by people who are both inexperienced drinkers and inexperienced drivers is really, really dangerous.
Setting the minimum legal drinking age at 21 also encourages disrespect for the law and encourages young adults to acquire and use false identification documents, which is not a social practice we want to encourage just right now. Moreover, that policy insultingly treats people who are adults for all other purposes as if they were still children, and deprives them of lawful access to an activity that forms part of the normal U.S. social scene and which some of them enjoy. And it may (the evidence isn’t clear) lead those who are drinking illegally rather than legally to do so irresponsibly rather than responsibly.
Now, given those facts, what do you want to do about it?
His solution is to implement zero tolerance laws for drinking and driving for people under 21 and raise alcohol taxes.
Megan McArdle suggests adding special licenses for people who have been convicted of drunk driving and making it illegal to serve them alcohol.
In the “not always right, but always certain” department, a contributor to the Free Press offers these pearls:
The problem with asking at what age it ought to be legal to drink is that it is a fundamentally perverse question. The “logic” of law is that it allows government the power to punish actions deemed harmful while restraining government officials from singling out disfavored individuals or groups and imposing sanctions on them. The “rule of law” requires that all laws take the form of truly general rules of action, rules that provide punishment for anybody who takes the prohibited action.
Government decisions that just pick an individual and impose a sanction on that individual are bills of attainder, and our Constitution prohibits them. Rules that single out subsets of the population and punish them for actions which are not illegal when taken by other people are pseudo-laws, and legitimate government has no authority to enact them. (Example: Women cannot work as bartenders.)
To ask at what age it should be legal to drink, therefore, flies in the face of the inherent nature of law as a general rule of action. Either drinking must be legal for all, or illegal for all. The latter approach was tried during Prohibition, and it caused horrible results: organized crime, corruption, etc. Wisely, Prohibition was repealed by the 21st amendment in 1933.