Colorado legalized marijuana for those over 21 in a ballot initiative last year, but exactly how the state would regulate the sale, advertising, and use of marijuana was unclear until Tuesday. The Marijuana Enforcement Division of the Colorado's Department of Revenue released a 136-page document [PDF] laying out how it will deal with weed. Marijuana sellers will be able to advertise on Coloradans' TVs, newspapers, and radio stations. But state and local ballot initiatives in Denver specifically could create significant taxes on marijuana sales.

For marijuana advertising, Colorado will enforce rules very similar to the alcohol industry's self-regulation. Ads will be allowed on TV, newspapers, and radio as long as the advertisers have "reliable evidence" that fewer than 30 percent of the expected audience is under 21 years old. So the newspaper ad pictured at right would be OK. But public weeds ads — like billboards and park benches, and other stuff visible from the street — will be prohibited. So perhaps the taxi cab ad pictured below would be banned. Out-of-state advertising won't be allowed. Sellers must not promote marijuana tourism.

It seems the same would go for this billboard outside of the Denver Broncos' NFL stadium during a game last Thursday night. This more aggressively anti-alcohol, pro-weed message would be hard for anyone to miss.

Note how the billboard uses classic beer-drinking imagery to pitch marijuana to a wider audience. Colorado's advertising regulations mark the beginning of the creation of what will someday be tedious weed advertising tropes. What's the marijuana version of the beer ad girl? Who will become the Most Interesting Man in the Weed World? 

Those advertisers might have to overcome some price hurdles, though, to bring in more customers. If a Colorado ballot initiative passes, marijuana buyers will have to pay a 15 percent excise tax, as well as up to an addition 15 percent sales tax. Similarly, a Denver city ballot issue would tack on a 3.5 percent tax on marijuana and give the city government the ability to raise that up to 15 percent, all on top of the state tax initiatives.

On Monday, Denver residents enjoyed a free joint giveaway, part of a protest against the proposed taxes.

Free marijuana being handed out in Denver to protest a possible 30% tax on recreational weed. pic.twitter.com/AMtpDcACRP - @CRepp28

— 7NEWS Denver Channel (@DenverChannel) September 9, 2013

The city claims that revenue from marijuana sales taxes will go to paying for local and state public services, including schools and police. But plenty showed up for the protest, or, at least on behalf of the free joints.

The Denver Post has a great slideshow of photos from the event, during which all 600 pre-rolled blunts were passed out, forcing the organizers to "furiously" roll more on top of a parked car to please the crowd.

Importantly, no arrests were made despite the very public smoking of some of those joints — open consumption remains illegal — a fact that the Denver city council criticized. Why go to all the trouble of making laws on marijuana if it will just be passed out willy-nilly?, they asked. Denver police have thus refused to enforce their own existing laws, so it remains to be seen whether these new Colorado rules will actually be enforced either. Those billboards and top-of-car ads just might be able to stay up, at least if enforcement is lax.

Colorado's rules for marijuana certainly remain in flux, and a Senate Committee today is addressing the "growing tension" between state and federal enforcement on the issue. Without a joint agreement between those two — and local police, too — there will surely be plenty more public joints.

(Photo of billboard: REUTERS/Rick Wilking)