President Obama responded last week to the most popular question submitted by online voters - whether marijuana should be made legal in order to bring this huge underground industry into the legal economy - by treating it pretty much as a joke.

But the time for jokes has passed. Our marijuana laws are killing people.

The horrifying drug-war violence on our southern border continues to worsen: beheadings, daily killings that now number more than 6,000, and honest officials fearing for their lives. U.S. marijuana laws subsidize these murderous gangs.

Some 60 to 70 percent of the profits that fuel the Mexican cartels come from marijuana. The chief of the U.S. Drug Enforcement Administration's Mexico and Central America Section recently told the New York Times that marijuana is the "king crop" for Mexican cartels, which have active operations in 230 U.S. cities.

Like it or not, marijuana is a massive industry. Some 100 million Americans admit to government survey-takers that they've used it, with nearly 15 million acknowledging use in the past month. That's a huge market - more Americans smoking pot than will buy a new car or truck this year.

U.S. policies are based on the fantasy that we can somehow make this industry go away, but prohibition hasn't stopped marijuana use. Indeed, federal statistics show a roughly 4,000 percent rise since the first national ban took effect in 1937. We've simply handed a virtual monopoly on production and distribution to criminals, including those brutal Mexican gangs.

The solution is obvious. After all, there's a reason these gangs aren't smuggling wine grapes. Prohibition simply doesn't work - not in the 1930s and not now.

End prohibition, and our marijuana industry could start to look like California's wine business: A responsible industry that adds to the state's prestige, tourism and tax coffers, rather than a source of violence and instability.