There’s a myth in this country that the drinking age is 21. But that’s only the legal age. The fact that government says you can’t drink before 21 does not mean younger people don’t drink.

More than 100 college presidents understand this, and now they want the minimum drinking age reconsidered.

“The 21-year-old drinking age is not working,” says the Amethyst Initiative, launched by former Middlebury College President John McCardell, president of Choose Responsibility Inc.

The college leaders’ statement charges that a “culture of dangerous, clandestine ‘binge-drinking’ — often conducted off-campus — has developed” and that “By choosing to use fake IDs, students make ethical compromises that erode respect for the law.”

It makes the obvious point that 18-21-year-olds are “deemed capable of voting, signing contracts, serving on juries and enlisting in the military, but are told they are not mature enough to have a beer.”

States started raising the drinking age to 21 in 1984, after Congress passed a law that stopped federal highway money from going to states that kept the age at 18. Curiously, the law was backed by President Reagan, a self-proclaimed advocate of federalism. Federalism presumes that we’ll get better laws if states are free to compete in making public policy. Federal mandates kill useful experimentation by enacting one-size-fits-all policies.

The college presidents make a lot of sense. Forbidding things like underage drinking or smoking marijuana doesn’t stop them from happening. The activity is just driven underground, where it is less subject to constructive social convention.

Of course, the Amethyst Initiative statement was angrily denounced by the usual activist groups that believe the answer to every problem is strict laws. Mothers Against Drunk Driving said the college presidents “have signed on to a misguided initiative that uses deliberately misleading information to confuse the public on the effectiveness of 21 law.” MADD cites a National Highway Traffic Safety Administration estimate that the higher drinking age “reduced traffic fatalities involving drivers 18 to 20 years old by 13 percent and has saved an estimated 25,509 lives since 1975.”

MADD also claims that “In most countries with lower drinking ages, intoxication is much more common among young people than in the United States.”

But does the “21 Law” really save lives or reduce intoxication? Choose Responsibility responds, “Depending on where you look, you’ll find many different numbers, all attributed to ‘science.’ What ‘science’? In fact, the statistic(s) cited are the result of a simple mathematical formula ... [that] takes 13 percent of the difference between one year’s alcohol-related traffic fatalities and the next and attributes the product to the 21-year-old drinking age. Recent research has called the consistent application of this formula into question.”

Even if MADD’s claims are right, McCardell counters that studies also show that those students who drink do so in more dangerous ways than they might if drinking could be done in the open.

Jordan Ballor of the Acton Institute for the Study of Religion and Liberty adds: “[C]ulture has a lot to do with how people respond to newfound freedoms or possibilities. ... Where the use of alcohol is not a taboo that can become part and parcel of a young-adult ‘rebellion’ experience, it seems less likely that binge drinking will function as a gateway to adulthood.”

I agree. We grow into adulthood, but laws like the 21-year-old drinking age presume that individuals change from child to adult at the stroke of midnight on their 21st birthdays. That’s nonsense.

What about MADD’s claim that intoxication is more common in countries with lower drinking ages? It’s not true, says anthropology professor Dwight Heath of Brown University: “In countries where people start to drink at an early age, alcohol is not a mystical, magical thing,” and they are not prone to “drink to get drunk. ...” He adds that “Several years ago, a study at the University of North Carolina found that ‘[D]rinking with parents appears to have a protective effect on general drinking trends.’ ...

“The fear that teaching kids to be responsible drinkers will only teach them to be heavy drinkers has been unfounded in Italy, Spain and other ‘wine cultures.’” Bring back federalism.

(John Stossel is co-anchor of ABC News’ “20/20” and an author.)