OKLAHOMA CITY (AP) — State referendums that have legalized medicinal or recreational marijuana have encouraged an Oklahoma-based electronic cigarette retailer to try to build a national franchise.

Voters in Oregon, Alaska and Washington, D.C., approved ballot measures Tuesday for recreational pot use. They join more than a dozen states where marijuana already use is legal in some form.

Chip Paul, CEO and co-founder of Tulsa-based Palm Beach, says the growing legalization opens the door for his company to market a method for producing a cannabis oil vapor product that can be inhaled through an e-cigarette. He is seeking to patent the method.

An Oklahoma Bureau of Narcotics and Dangerous Drugs spokesman says the agency is concerned about the inhalation of cannabis oils via e-cigarettes and says it’s a way to disguise illegal marijuana use.