DENVER (CBS4) – The statewide amendment to legalize marijuana use for adults in Colorado has passed.

Amendment 64 supporters were ecstatic at their gathering in Denver Tuesday night when news came down.

“Marijuana prohibition has failed in Colorado and it has failed in all sorts of other places,” Amendment 64 advocacy director Betty Aldworth told CBS4. “I’m so proud and so honored to have worked with this team of people and to live in a state where people recognize marijuana prohibition is a failure and we can do better.”

The amendment allows adults over 21 to possess as much as an ounce of pot. It also allows people to grow as many as six pot plants in secure, private areas.

Supporters believe legalization will generate tens of millions of dollars in tax revenue for Colorado.

The approval of the amendment puts Colorado in defiance of federal drug law.

“It’s still against federal law,” Gov. John Hickenlooper told CBS News anchor Scott Pelley about an hour later. “I’m not sure we can make it as legal as the voters would like us to do. But clearly the will of the voters spoke.”

Hickenlooper, who opposed the measure, said it’s “not immediately apparent” how the amendment will hold up against the national law.

Jeff Dorschner, spokesman for the U.S. Attorney’s office released a statement after the measure’s passage, saying the “Department of Justice’s enforcement of the Controlled Substances Act remains unchanged.”

“In enacting the Controlled Substances Act, Congress determined that marijuana is a Schedule I controlled substance. We are reviewing the ballot initiative and have no additional comment at this time,” Dorschner said.

State voters rejected recreational pot in 2006, but Aldworth said this measure comes at a time when voters have a different mindset, thanks in part to the burgeoning medical marijuana industry in several areas of the state.

“Amendment 64 is quite different from Amendment 44 in 2006 in that it envisions the regulated model for marijuana sales whereas Amendment 44 only decriminalized for adult use,” she said. “What we know is that Colorado voters have accepted the idea that we can regulate marijuana like alcohol successfully and we can make a safer, healthier and more just Colorado by doing so.”

The measure had the backing of the NAACP, the ACLU and the state public defender’s office, but most major state leaders came out in opposition.

Roger Sherman, the No on 64 campaign director, released a statement just after 9 p.m. on Election Day conceding the race:

“We knew all along this was an uphill battle against a well-funded national movement. We appreciate the efforts of Governor John Hickenlooper, former Governors Bill Owens and Bill Ritter, Attorney General John Suthers, Mayors Michael Hancock and Steve Hogan and countless other sheriffs, county commissioners, district attorneys and local elected officials who joined with the business community and citizens of Colorado to oppose this ill-conceived amendment.

“We can only hope that our concerns and fears about amending the Constitution to make Colorado the first state to legalize the recreational use of marijuana do not come true.”

The states of Oregon and Washington also had pot legalization amendments on the ballot, and at least one of those states — Washington — also approved their measure.

Colorado is already one of 17 states that allow marijuana use by people with certain medical conditions.