Six Colorado county sheriffs are suing their governor over the state's recreational marijuana law, and law enforcement officials from Kansas and Nebraska are also fighting the legislation.

Colorado's recreational marijuana business lit up after voters made it legal 14 months ago, CBS News' Mark Strassmann reports.

Stores like Medicine Man in Aurora, just outside Denver, generated more than $300 million in sales last year alone. But pot is still considered illegal under federal drug laws.

Larimer County Sheriff Justin Smith said his deputies feel handcuffed.

"If I defend and uphold the rights of an individual under Colorado Constitution to have marijuana, then that puts me in violation of my oath of office on the federal end," Smith said.

Smith called it a "crisis of conscience," and the lawsuit asks a federal judge to strike down the law and close more than 300 licensed retail marijuana stores.

"There is nothing that requires Colorado to enforce federal marijuana laws," Marijuana Policy Project communication director Mason Tvert said.

"Colorado is taking steps to control it. These guys are taking steps to bring back an underground market," Tvert said.

It's estimated that nearly half of Colorado's recreational marijuana buyers come from other states, where pot is illegal. Law enforcement officials from Nebraska and Kansas, two of Colorado's neighbors, have joined the suit, saying they've been overwhelmed by illegal drug activity that flows across Colorado's border.

"On traffic stops they're coming up with a lot of marijuana coming through, which requires the arrest time, the prosecution time, the jail time, the prison time," Smith said.

But marijuana supporters say authorities should focus on serious crime.

"If these sheriffs are unable to figure out the difference between these state and federal laws, they're really not fit to be law enforcement officials," Tvert said.

Colorado Gov. John Hickenlooper said the state will continue to defend its marijuana law despite this being the fourth lawsuit challenging it.

Marijuana is both legal in Colorado and still under fire.