Vermont Sen. Patrick Leahy is demanding Congressional hearings in September to address the growing divide between state and federal marijuana laws.

With twenty states now having legalized the medical use of cannabis — and two additional states having legalized non-medical marijuana production and retail sales — Congress and the Obama administration have little choice but to acknowledge this rapidly changing reality.

The general public has ‘evolved’ on the issue of cannabis and cannabis policy. Their political leaders will soon little choice but to follow.

Writing in a recently published report by the Washington, DC think-tank The Brookings Institute, authors E.J. Dionne and William Galston concluded, “In less than a decade, public opinion has shifted dramatically toward support for the legalization of marijuana. … Demographic change and widespread public experience using marijuana imply that opposition to legalization will never again return to the levels seen in the 1980s. The strong consensus that formed the foundation for many of today’s stringent marijuana laws has crumbled.”

It certainly has. Never in modern history has there existed greater public support for ending the nation's nearly century-long experiment with pot prohibition and replacing it with a system legalization and regulation. The proof is in the polls – and at the ballot box.

In November, 55 percent of voters in two states, Colorado and Washington, decided in favor of measures legalizing the personal use, commercial production, and retail sales of cannabis to adults over the age of 21. Perhaps most notably, in Colorado, pot proved to be far more popular with voters than did the President! In the months since these historic votes, national public support for marijuana law reform has only gained momentum.

According to a recent Reason Magazine-Rupe nationwide survey, more than nine out of ten US adults say that people who possess or consume small quantities of cannabis should not face jail time.

A May 2013 nationwide Fox News telephone poll reported that 85 percent of voters support allowing adults to use cannabis for therapeutic purposes. The total is an increase in support of four percent since Fox last polled the question in 2010 and is the highest level of public support for the issue ever reported in a scientific poll.

Moreover, a highly publicized national survey recently commissioned by the Pew Research Center reports that 72 percent of Americans now believe that "government efforts to enforce marijuana laws cost more than they are worth.” Sixty percent of Americans say that the government should no longer enforce federal anti-marijuana laws in states that have approved of its use.

Likewise, a December 2012 Angus Reid national sampling of US voters, 66 percent of Americans say that they expect cannabis to be legal within the next ten years.

But Americans may not have to wait that long. Ballot measures to legalize and regulate the plant’s adult use are expected in several additional states, including Alaska, California, Maine, and Oregon. Voters in these and other states are already on board. Recently published polls by survey leaders Gallup, Pew, Quinnipiac University, and Public Policy Polling all find that far more Americans now favor legalizing marijuana for adults than believe in its continued prohibition. Why the dramatic shift in public opinion? The answer should be obvious. The ongoing enforcement of cannabis prohibition financially burdens taxpayers, encroaches upon civil liberties, engenders disrespect for the law, impedes legitimate scientific research into the plant's medicinal properties, and disproportionately impacts communities of color. Furthermore, the criminalization of cannabis simply doesn't work.

Despite more than 70 years of federal prohibition, Americans' consumption of and demand for cannabis is here to stay. It is time for America’s public policies to reflect this reality. Unlike the federal government, which continues to stubbornly define cannabis as an illegal commodity that is as equally dangerous as heroin, a majority of voters now recognize that pragmatic regulatory framework that allows for the licensed commercial production and sale of cannabis to adults but restricts use among young people best reduces the risks associated with the plant’s use or abuse. The public has gotten message. Next month we’ll learn whether or not the administration has also received the memo.

Marijuana legalization is no longer a matter of ‘if’; it’s a matter of ‘when.’