TULSA, Oklahoma - The legalization of medical marijuana comes with a big issue for Oklahoma's gun owners. If you want to get medical marijuana, you can't own or buy a gun. 

Federal law prohibits any person who is an "unlawful user of or addicted to any controlled substance" from possessing firearms or ammunition. The law covers everything from owning, shipping, transporting or receiving any firearms or ammunition.

There are no exceptions in the law for medical marijuana users.

Some gun shop owners we talked to are a little concerned. 

"That was my initial reaction - my gosh, we might lose some business," said Austin Warfield, owner of C.O.P.S. Gun Shop.

"We might lose some gun sales because if someone has a medical marijuana card, they won't be able to purchase a gun." 

Warfield said they will be making sure any transaction in their store is legal.

"Well, they fill out the state or federal form 4473 background check," he said. "On that form is a question, are you addicted to marijuana or any other drugs."

Question 11.e. on that form asks:

Are you an unlawful user of, or addicted to, marijuana or any depressant, stimulant, narcotic drug, or any other controlled substance?
Warning: The use or possession of marijuana remains unlawful under Federal law regardless of whether it has been legalized or decriminalized for medicinal or recreational purposes in the state where you reside.

The ATF recommends current gun owners make a plan about what they are going to do with their weapons before getting a medical marijuana license.