On Tuesday, the Senate Judiciary Committee will hold a first-ever Senate hearing on the issue of marijuana legalization and the tension between state and federal marijuana laws. Last November, Colorado and Washington became the first political jurisdictions in the world to approve the legal regulation of marijuana. Twenty states and the District of Columbia have also approved the medical use of marijuana. On August 29, the Department of Justice issued a directive to federal prosecutors instructing them not to interfere with state marijuana laws – as long as a number of stipulations are adhered to, such as preventing distribution to minors.

“On the one hand, it’s hard to fathom why the Senate had to wait until twenty states had legalized marijuana for medical purposes, and two more had legalized it more broadly, before taking up this issue for the first time,’ said Ethan Nadelmann, executive director of the Drug Policy Alliance. “But, that said, Senator Leahy’s leadership on this issue is highly welcome, and suggests that the Senate at last is acknowledging the remarkable shift in public opinion and state laws involving marijuana.”

More than 750,000 people were arrested for marijuana in the U.S. in 2011, the last year for which data is available. Of those arrests, 87% were for mere possession. Polls show that a majority of Americans support legalizing and regulating marijuana like alcohol, and support is rising across the political spectrum. It is likely that more states will legalize marijuana between now and November 2016.

Support is increasing in Congress for changing federal marijuana policies. Last week, Senator John McCain (R-AZ) made headlines when he said, “Maybe we should legalize [marijuana]. We're certainly moving that way as far as marijuana is concerned. I respect the will of the people.” Senate Judiciary Chairman Patrick Leahy (D-VT) has said the federal government “ought to respect” states that legalize and regulate marijuana. Senator Rand Paul (R-KY) has suggested decriminalizing all drug users, including marijuana users. A number of senators voted to prohibit the Drug Enforcement Administration (DEA) from spending any money undermining state medical marijuana laws when they were members of the U.S. House – Senators Jeff Flake (R-AZ), Christopher Murphy (D-CT), Mazie Hirono (D-HI), Martin Heinrich (D-NM), Tammy Baldwin (D-WI).

Meanwhile, in the House, nine bipartisan marijuana law reform bills have been introduced, including two bills that would end federal marijuana prohibition. 163 Representatives voted last year to prohibit the DEA from undermining state medical marijuana laws, including 28 Republicans. Earlier this year 225 House members approved a successful amendment allowing colleges and universities to grow industrial hemp for research purposes, if it’s legal under state law.

In late August, Attorney General Eric Holder announced that he informed the governors of Washington and Colorado that the Department of Justice will allow the states to implement their ballot initiatives that legalized the production, distribution, and sale of marijuana for adults. Deputy Attorney General James Cole also issued a memo to U.S. attorneys across the country outlining priorities for federal prosecutors enforcing marijuana laws. In a surprising twist, the memo notes that state regulation may further federal interests by reducing organized crime and making marijuana less available to youth.

“Legalizing marijuana and shrinking the number of people behind bars in the U.S. is an issue the left and right can join together on,” said Bill Piper, director of national affairs for the Drug Policy Alliance. “Like the repeal of alcohol prohibition, the repeal of marijuana prohibition will save taxpayer money, put organized crime syndicates out of business, and protect the safety of young people.”