Marijuana seized by Deuel County (Neb.) sheriff’s deputies is stacked in an unused jail cell in the county courthouse June 2, 2014.(Photo: Trevor Hughes, USA TODAY)

DENVER — Sheriffs from Colorado and neighboring states Kansas and Nebraska say in a lawsuit to be filed Thursday that Colorado’s marijuana law creates a “crisis of conscience” by pitting the state law against the Constitution and puts an economic burden on other states.

The lawsuit asks a federal court in Denver to strike down Colorado’s Amendment 64 that legalized the sale of recreational marijuana and to close the state’s more than 330 licensed marijuana stores.

Lead plaintiff, Larimer County, Colo., Sheriff Justin Smith, calls the case a “constitutional showdown.” Each day, he says, he must decide whether to violate the Colorado Constitution or the U.S. Constitution. Colorado legalized recreational marijuana sales Jan. 1, 2014, but marijuana remains illegal at the federal level.

Colorado is “asking every peace officer to violate their oath,” Smith said. “What we’re being forced to do … makes me ineligible for office. Which constitution are we supposed to uphold?”

The out-of-state sheriffs say the flow of Colorado’s legal marijuana across the border has increased drug arrests, overburdened police and courts and cost them money in overtime.

Felony drug arrests in the town of Chappell in Deuel County, Neb., 7 miles north of the Colorado border, jumped 400% over…