As a teenager, Barack Obama liked to get high in the back of a friend's VW bus. His hallmark: a smoking technique he called Total Absorption. He knows, as did George W. Bush and Bill Clinton before him, what we all know: that pot is essentially harmless. Yet the government continues to wage a senseless and costly war on marijuana, treating pot as if it were more dangerous than crack cocaine.

More than 750,000 Americans were arrested on marijuana charges last year – 87 percent for simple possession. The costs of prohibition are staggering – nearly $8 billion a year wasted on police and prisons alone, with billions more squandered by not taxing pot like tobacco or alcohol. In Mexico – where nearly two-thirds of the pot smoked in this country originates – drug violence has claimed nearly 50,000 lives since 2006. Yet all the while, demand for pot has increased like wildfire: Nearly 30 million Americans enjoyed pot at least once last year.

Mr. President, this war is a sham, a folly, a colossal waste of money and human potential. And you can end it with a few strokes of your pen. Through executive order, you can advance life, liberty and the pursuit of happiness, and begin to bring another mindless war to a responsible conclusion. All it requires is the same courage you displayed on gay marriage. Simply say what's in your heart – what you know to be true.