Whatever your views on firearms, there’s no denying that gun ownership is a fundamental right. One Gallup poll estimates that Americans own nearly 400 million firearms, which equates into more guns than people.

But few rights are absolute. Those who cannot legally receive or possess a firearm include convicted felons, fugitives from justice, someone who receives a dishonorable military discharge and those with domestic violence convictions. That list also includes marijuana users, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Advocates for legalized cannabis get a little huffy when reminded that legalization of marijuana is not absolute. The biggest problem is the disconnect between state laws, which are becoming more permissive, and federal law that lists marijuana as a Schedule 1 substance on par with LSD and heroin.

That impacts firearms possession and purchases from licensed dealers, because of Form 4473. This asks whether the buyer is an “unlawful user of or addicted to any controlled substances.” If you lie on a federal application, you’ve committed a felony. If you’re truthful, the transaction can be denied.

The state of Pennsylvania pulls no punches in information provided to medical marijuana cardholders in that state: “To clarify, even if state law permits the use of medical or recreational marijuana, federal law prohibits marijuana users from using or purchasing a firearm. It’s as simple as that.”

For legal marijuana users, there is some ambiguity in states, like Missouri, where background checks are not required to buy a gun from a private, unlicensed dealer. But that gun owner could run into problems down the line because the federal law also addresses possession of firearms.

The short-term question becomes one of enforcement. It’s unlikely that police or the ATF will crosscheck the marijuana cardholder registry with a database of gun owners. In fact, an ATF official previously told this newspaper that would not happen. They are not coming for your guns.

But the issue will come up in connection with arrests for illegal activity and contact with law enforcement. In Missouri, regulations make it clear that state and local law enforcement can access the marijuana registry, upon request and only to verify a particular individual.

Some states have tried to clarify that departments of public safety cannot share confidential information in a marijuana registry. Others allow marijuana cardholders to have conceal-carry permits, which is just a piece of paper without a gun.

This just nips around the edges. In Missouri, those who qualify for medical marijuana should be ready to make a difficult choice until Congress finally addresses the mixed messages on cannabis.