Call it a public service announcement: you can't legally buy a gun in Colorado and be a legal pot user.

Yes, marijuana is legal here and in many other states, but the feds don't see it that way. They’re coming out with an update to a form you should fill out - truthfully - when buying a gun.

“So far as marijuana is concerned, it's still a controlled substance federally,” said Paul Brown, director of Industry Operations at the Denver Division of the Bureau of Alcohol, Tobacco, Firearms and Explosives. “There's been a lot of changes lately with marijuana laws across the nation and this provides an opportunity, with the changing of the form, to ensure that dealers and purchasers know exactly what federal law is in relation to this topic.”

It so happens, the ATF was already changing its most important form, the Firearms Transaction Record, effective this coming January. Colorado has universal background checks, which means, with a few exceptions, gun buyers must complete a background check, hence this form.

The timing of the form change just happened to coincide with multiple states voting on legalizing marijuana use. The ATF form asks if you're an "unlawful user" of marijuana, and before you in Colorado check “no," it reminds you of the federal government position on the matter.

“The use or possession of marijuana remains unlawful under federal law, whether is related to recreational or medical use,” Brown said.

“I've always thought the government's position on marijuana is archaic,” said Rachel Gillette, who manages the Cannabis Practice Group in the Denver Office of Greenspoon Marder. “That they continue to deny the medical efficacy of marijuana, that they don’t seem to appreciate the realities of people who consume marijuana and can consume it responsibly, and they can also be responsible gun owners.”

Gillette said that post-election, 29 states plus the District of Columbia passed medical marijuana legislation and eight of those passed recreational adult use.

“To say that somebody can be on a no-fly list and still possess a firearm, but yet if they are taking medical marijuana under their doctor's supervision and under a state medical program, they can't own a firearm, I think there's something inherently shocking about that,” Gillette said.

A debate on that is for another story.

This is just a friendly heads up that, lying on a federal form is a crime. Just FYI.