The measure, which would legalize possession of small amounts of marijuana by adults, is one of two that will go to voters in November after a Washington state initiative to legalize pot earned enough signatures last month to qualify for the ballot there.
"This could be a watershed year in the decades-long struggle to end marijuana prohibition in this country," Art Way, Colorado manager of the Drug Policy Alliance, said in a statement. The Alliance supports the initiative.
"Marijuana prohibition is counterproductive to the health and public safety of our communities. It fuels a massive, increasingly brutal underground economy, wastes billions of dollars in scarce law enforcement resources, and makes criminals out of millions of otherwise law-abiding citizens."
Colorado is one of 16 states and the nation's capital that already allow marijuana use for medical purposes even as cannabis remains classified as an illegal narcotic under federal law - and public opinion is sharply divided on the merits of full legalization.
No states allow marijuana for recreational use, and California voters turned back a ballot initiative to legalize the drug for such use in 2010, in part because of concerns about how production and sale of the drug would be regulated.
Since then, the U.S. Department of Justice has cracked down on medical cannabis operations in several mostly western states including Colorado and Washington, raiding dispensaries and growing operations and threatening landlords with prosecution.
A spokesman for Colorado Attorney General John Suthers said on Monday that the office opposes the legalization proposal.
"The attorney general will oppose any measure that makes marijuana more accessible," spokesman Mike Saccone said.
The Colorado measure, if approved by voters, would legalize possession of up to an ounce of marijuana or up to six plants for cultivation, said Mason Tvert, co-founder of the Campaign to Regulate Marijuana Like Alcohol.
It would also set up a regulatory framework for the sale of cannabis products and the application of sales and excise taxes, in addition to legalizing the cultivation of industrial hemp.
WOULD EARMARK TAX REVENUE FOR SCHOOLS
A provision of the measure would also annually earmark the first $40 million in tax revenue generated from pot sales to fund public school construction, Tvert said, although he could not estimate how many tax dollars would be generated.
Any remaining money over $40 million would go to the state's general fund, he said.
Colorado voters rejected a measure to legalize small amounts of cannabis in 2006, but Tvert said the new proposal with its taxing provision, and potential jobs created through the marijuana industry and peripheral businesses would make it more palatable to voters.
"The time is right," he said, citing a December poll by Public Policy Polling that showed 49 percent of Colorado voters now support legalization.
Nationwide, an October 2011 Gallup Poll that found a record 50 percent of Americans polled supported legalizing marijuana use, up from 36 percent five years earlier.
Under a medical marijuana law enacted in 2000, Colorado currently maintains a registry of more than 80,000 card-carrying patients and rules governing how physicians and distributors operate.
However, federal prosecutors launched a crackdown last month against nearly two dozen medical marijuana dispensaries located within 1,000 feet of schools, giving proprietors 45 days to cease operations or face civil and criminal penalties. That deadline lapsed on Monday.
Jeff Dorschner, spokesman for the U.S. Attorney's Office in Denver, said an investigation was underway to determine if the alleged violators complied with the ultimatum.
A second round of notifications to other pot dispensaries who federal authorities said were in violation of the 1,000-foot law will be notified "sooner rather than later," Dorschner said.
Proponents of legalized recreational possession initially submitted more than 163,000 signatures on a petition to place their measure on the ballot, but the state's secretary of state declared the petition insufficient on February 3.
Advocates then submitted an additional 14,000 signatures two weeks ago, and after a second review, the state certified that the proposal would qualify for the general election ballot on November 6, 2012.
(Writing by Steve Gorman; Editing by Dan Whitcomb and Cynthia Johnston)
