The biggest obstacle remains the federal government's classification of marijuana as a Schedule 1 substance, making it illegal for any use.

Still, look at the business facts:

A report out from Greenwave Advisors, a "comprehensive research and financial analysis for the emerging legalized marijuana industry," projects that legal cannabis could be an industry with revenues of $35 billion by 2020 if marijuana is legalized at the federal level. They note that this is a floor representing revenues in the first year of countrywide legalization.

To put that figure in perspective, $35 billion represents more annual revenue than the NFL (currently $10 billion), and is roughly on par with current revenues for the newspaper publishing industry ($38 billion) and the confectionary industry ($34 billion).

Greenwave arrived at its numbers by considering existing and likely marijuana markets - medical and recreational - in states that already have them, as well as states that appear likely to open up such markets by 2020.According to the Huffington Post, Greenwave assumes 12 states plus DC will have legalized recreational marijuana in that time, with medical marijuana markets in 37 states. Currently 23 states have legalized medical marijuana, and two have legalized the plant for recreational use. Even without full federal legalization, Greenwave projects legal marijuana revenues of $21 billion.

It's worth noting that there's a fair degree of uncertainty surrounding these numbers - current estimates place the size of the U.S. black market at anywhere from 10 to 120 billion dollars. Predicting future marijuana sales may be a fool's errand, as evidenced by Colorado's difficulties in projecting marijuana tax revenues earlier this year.

Considering the legal marijuana industry generated roughly $1.53 billion in revenues in 2013, according to industry research group Arcview Market Research, it's reasonable to assume there's a lot of growth potential between now and then.

...

Contrary to dire warnings by marijuana prohibitionists, legalization has so far been a non-event. The most discernable change in Colorado has come in the form of $45 million in marijuana tax revenues so far this year, high enough that the state government now must consider whether to refund some of it.