The law is clear, Colorado’s legal marijuana must stay within state borders. While most customers receive this warning when visiting a dispensary, many of them appear not to heed it.

Since Colorado legalized weed in 2012, law enforcement officials at the state’s border with Nebraska have been busy trying to intercept illegal exports. Last month, they booked 23 cases of drivers trying to smuggle everything from weed to paraphernalia to edibles, like gummy bears—all of which become illegal once they reach Nebraska.

Sheriff Adam Hayward, who patrols the main highway between the two states, says most drivers are pulled over for basic traffic violations, and then the scent of weed gives them away. “The smell is just overwhelming when they roll the window down,” he says.

In Nebraska, the penalties for weed possession range from a $300 fine to up to five years in prison and a $10,000 fine, depending on amount. Hayward says he recently confiscated six pounds of marijuana, purchased legally from a Colorado dispensary. The driver, who planned to sell the goods in Nebraska, was convicted on felony charges.

Drivers are also increasingly getting busted on charges of driving under the influence of drugs. “They’re using it while they’re driving,” says Sheriff Hayward. “It’s a risk to themselves to drive that way, but it also puts the rest of the motoring public at risk if they’re on the roadway at the same time.”