DENVER — Ten sheriffs from three different states sued Colorado Thursday for decriminalizing marijuana — joining a handful of recent legal challenges urging courts to strike down the state’s legalization of recreational pot. The sheriffs from Colorado, Kansas and Nebraska say that Colorado’s 2012 marijuana legalization vote violates federal law. “A state may not establish its own policy that is directly counter to federal policy against trafficking in controlled substance,” the sheriffs argue in the lawsuit filed in U.S. District Court in Denver. The lawsuit is the latest legal challenge to legal weed. Nebraska and Oklahoma have appealed to the U.S. Supreme Court to strike down marijuana legalization in Colorado. The Supreme Court hasn’t said yet whether it will hear that case. A group of Colorado residents have filed their own federal challenge, saying marijuana reduces property values. The sheriffs note that more than half of Colorado’s recreational pot sales last year were sold to out-of-state visitors, according to data from Colorado’s marijuana regulators. The sheriffs say the weed is spilling across state lines. Even in Colorado, the sheriffs say, legal weed forces police officers to violate federal drug law. “The scheme enacted by Colorado for retail marijuana is contrary and obstructive” to federal drug laws, the sheriffs argue. Marijuana legalization opponents joined a news conference in Washington, D.C., Thursday and praised the legal challenges. “Although states should be able to determine appropriate penalties, we need uniform federal drug laws regarding legalization,” Kevin Sabet, head of the group Smart Approaches to Marijuana, said in a statement. But the lawsuit was brushed off by others, including U.S. Rep. Jared Polis, a Colorado Democrat who supports legal marijuana. “This lawsuit is a silly attempt to circumvent the will of Colorado voters and is a waste of time,” Polis said in a statement. The Colorado plaintiffs are Larimer County Sheriff Justin Smith, Yuma County Sheriff Chad Day, Elbert County Sheriff Shayne Herp, Hinsdale County Sheriff Ronald Bruce, Kiowa County Sheriff Casey Sheridan and Delta County sheriff Frederick McKee. The Nebraska plaintiffs are Deuel County Sheriff Adam Hayward, Deuel County Attorney Paul Shaub, Cheyenne County Sheriff John Jenson and Scotts Bluff County Sheriff Mark Overman. The Kansas plaintiffs are Sherman County Sheriff Burton Pianalto and Charles Moser, attorney for Sherman, Wallace and Greeley counties. Colorado’s attorney general’s office, which will defend the state pot law in all three lawsuits, did not immediately respond to the sheriffs’ filing Thursday. Colorado has until March 27 to respond to the lawsuit from Nebraska and Oklahoma.