It's been nearly 25 years since Congress blackmailed the states to raise the minimum drinking age to 21 or lose federal highway funding. Supporters of the law have hailed it as an unqualified success, and until recently, they've met little resistance.

For obvious reasons, no one wants to stand up for teen drinking. The alcohol industry won't touch the federal minimum drinking age, having been sufficiently scolded by groups like Mothers Against Drunk Driving and federal regulators. So the law's miraculous effects have generally gone unchallenged.

But that may be changing. Led by John McCardell, the soft-spoken former president of Middlebury in Vermont, a new group called the Amethyst Initiative; is calling for a new national debate on the drinking age. And McCardell and his colleagues ought to know. The Amethyst Group consists of current and former college and university presidents, and they say the federal minimum drinking age has contributed to an epidemic of binge drinking, as well as other excessive, unhealthy drinking habits on their campuses.

This makes perfect sense. Prohibitions have always provoked over-indulgence. Those of us who have attended college over the last 25 years can certainly attest to the fact that the law has done nothing to diminish freshman and sophomore access to alcohol. It has only pushed underage consumption underground. It causes other problems, too. Underage students, for example, may be reluctant to obtain medical aid for peers who have had too much to drink, out of fear of implicating themselves for drinking illegally, or for contributing to underage drinking.

More than 120 college presidents and chancellors have now signed on to the Amethyst Initiative's statement, including those from Duke, Tufts, Dartmouth, Johns Hopkins, Syracuse, Maryland, and Ohio. Over the last few years several states, including Wisconsin, Montana, Minnesota, Kentucky, South Carolina, and Vermont have also considering lowering their drinking ages back to 18.

All of this has the usual suspects predictably agitated. Mothers Against Drunk Driving, not accustomed to striking a defensive posture, calls the Amethyst Initiative's request for an "informed debate" on the issue "deeply disappointing," and has even raised the possibility that parents shouldn't send their kids to colleges who have signed on to the measure.

Acting National Transportation Safety Board Chairman Mark Rosenker says it would be a "national tragedy" to, for example, allow 19- and 20-year-old men and women returning from Iraq and Afghanistan to have a beer in celebration of completing their tours of duty.

Supporters of the 21 minimum drinking age have long credited the law with the dramatic reduction in traffic fatalities they say took place after it was passed. But a study released last July may pull the rug out from their strongest argument.

The working paper by economic researchers Jeffrey Miron and Elina Tetelbaum finds that the bulk of studies on highway fatalities since the federal minimum drinking age went into effect erroneously include data from 12 states that had already set their drinking ages at 21, without federal coercion. That, Miron and Tetelbaum conclude, may have skewed the data, and indicated a national trend that may not actually exist.

While it's true that highway fatalities have dropped since 1984, it isn't necessarily because we rose the drinking age. In fact, the downward trend actually began in 1969, just as many states began lowering their drinking ages in recognition of the absurdity of prohibiting servicemen returning from Vietnam from enjoying a beer (the 1984 law was a backlash against those states). As Miron and Tetelbaum explain, 1969 was the year when "several landmark improvements were made in the accident avoidance and crash protection features of passenger cars," a more likely explanation for the drop than a law passed 15 years later.

Miron and Tetelbaum also credit advances in medical technology and trauma treatment for the decline in fatalities, which makes sense, given that we've seen improvements in just about every other area of human development over the same period, including life expectancy, and both incidence and survival rates of major medical conditions like heart disease, cancer, and stroke— none of which have much to do with teen drinking.

The U.S. has the highest minimum drinking age in the world (save for countries where it's forbidden entirely). In countries with a low or no national minimum drinking age, teens are introduced to alcohol gradually, moderately, and under the supervision of their parents.

U.S. teens, on the other hand, tend to first try alcohol in unsupervised environments — in cars, motels, or outdoor settings in high school, or in dorm rooms, fraternity parties, or house parties when they leave home to go to college. During alcohol prohibition, we saw how adults who imbibed under such conditions reacted — they drank way too much, way too fast. It shouldn't be surprising that teens react in much the same way.

Anti-alcohol organizations like MADD and the American Medical Association oppose even allowing parents to give minors alcohol in supervised settings, such as a glass of wine with dinner, or a beer on the couch while watching the football game. They've pushed for prison time for parents who throw supervised parties where minors are given access to alcohol, even though those parties probably made the roads safer than they otherwise would have been (let's face it — if the kids hadn't been drinking at the supervised party, they'd have been drinking at an unsupervised one). They advocate a "not one drop until 21" policy that's not only unrealistic, it mystifies and glorifies alcohol by making the drug a forbidden fruit—a surefire way to make teens want to taste it.

McCardell and the academics who have signed on to the Amethyst Initiative are asking only for a debate—an honest discussion based on data and common sense, not one tainted by Carry Nation-style fanaticism. In today's hyper-cautious, ban-happy public health environment, that's refreshing. The group comprises serious academics who have collectively spent thousands of years around the very young people these laws are affecting. The nation's policy makers would be foolish to dismiss their concerns out of hand.

Radley Balko is a senior editor for Reason magazine and maintains a personal blog at www.TheAgitator.com. Respond to this column at radley.responses@gmail.com.