Recreational Marijuana: Prosecutors, County Sheriffs Challenge Amendment 64

— -- County sheriffs and prosecutors from three states launched a court challenge today against Colorado’s legalized marijuana, claiming that huge amounts of weed crossing state lines is placing an “undue burden” on the resources of small departments.

Colorado voters passed Amendment 64 legalizing recreational marijuana in November 2012. Retail stores began selling weed January 1, 2014, but pot is still considered illegal by the federal government.

"Amendment 64 is preempted by federal law and therefore violates the Supremacy Clause (Article VI) of the United States Constitution,” according to the lawsuit, filed today in federal court.

The plaintiffs—six Colorado sheriffs, four Nebraska sheriffs along with two county attorneys from Nebraska and Kansas— want the relevant sections of the Colorado constitution declared “invalid, null, and void.”

Speaking at the National Press Club in Washington D.C. today, Sheriff Mark Overman of Scott’s Bluff County, Nebraska says Colorado’s marijuana is a burden on taxpayers in his jurisdiction.

“Colorado’s legalization of marijuana has completely changed the landscape involving the marijuana that we encounter,” he said. "Because of Amendment 64, our jails are full, our court dockets are full. There are increased costs for overtime, for incarceration.”

Overman also claims his deputies are busting more kids for pot.

“We are seeing a marked increase in the numbers of children as young as 13 that we are finding in possession of marijuana. We don’t want what Colorado has," he said.

Larimer County Colorado Sheriff Justin Smith also said legalized marijuana in his state has created a “constitutional showdown” for law enforcement.

“In Colorado every elected official, sheriffs included, are required under the state constitution to take an oath of office,” Smith said. “And that oath of office requires that they swear to defend the Constitution of the United States and the state of Colorado. Amendment 64 puts a conflict in those two parts of the oath of office.”

The Justice Department has said it will not take legal action against states that have approved recreational marijuana use.

Colorado Governor John Hickenlooper is named as the defendant in the lawsuit filed today.

Hickenlooper has not been formally served with the lawsuit, said his spokeswoman Kathy Green.

However, Green told ABC News, “We will continue to defend the will of the voters while prioritizing public safety.”

Marijuana advocates say the lawsuit is frivolous.

"These guys need to get over it,” said Mason Tvert with the Marijuana Policy Project.

"These law enforcement officers are trying to force marijuana cultivation and sales back into the underground market. Colorado adopted these laws in order to start controlling marijuana, and it's working,” Tvert told ABC News.

Recreational marijuana is now legal in Alaska, Colorado, Washington state and Washington, D.C.