DENVER – Despite growing public support for legalizing marijuana, a lawsuit filed by Nebraska and Oklahoma shows that at least two segments of American society are prepared to fight the idea before the nation’s highest court – social conservatives and law enforcement.

The lawsuit seeks to overturn Colorado’s experiment in legalized recreational pot, alleging that the two conservative states are being overrun with Colorado marijuana that is making it harder for them to enforce their own drug laws.

Nebraska Attorney General Jon Bruning framed it as a public-safety issue, though the complaint provides little data to support its claim that Colorado pot is pouring into neighboring states.

The case emerges at a time when polls show growing public support for legal weed. Even Congress this week started to ease restrictions on the drug, barring the federal government from interfering with the 23 states that allow it for medical uses.

National law-enforcement groups have staunchly opposed the legalization of marijuana. The lawsuit filed to the U.S. Supreme Court cheered some police in Colorado who have been frustrated at the public’s wide acceptance of that state’s recreational marijuana market, despite some examples of people overdosing on high-concentration edibles.

“When you work in the public-safety industry, you’re impacted by this all the time,” said Jim Gerhardt, vice president of the Colorado Drug Investigators Association. “We’re seeing it. The firefighters are seeing it. The hospitals are seeing it. But the general public can be apathetic.”

Mason Tvert, the pro-marijuana activist who helped push legalization in Colorado, said he was not surprised by the resistance from Oklahoma and Nebraska, two socially conservative states that were reluctant to repeal Prohibition.

“When you think about who are the two types of people who’d never want to try marijuana, it’s people who are looking at it morally, through religion ... and that law-enforcement attitude that this is the law, and we want to keep it,” Tvert said.

The legalization movement, he added, has seen some of its stiffest resistance in conservative, religious states in the Deep South and in Nebraska, where activists were unable to get enough signatures to put a medical-marijuana measure on the 2012 ballot.

Law-enforcement agencies have long said anecdotally that they are making more marijuana arrests and seizing more of the drug since Colorado voters legalized the drug. But there’s no way to know exactly how much legal pot is leaving the state.

In a recent report, the agency known as the Rocky Mountain High Intensity Drug Trafficking Area wrote that the amount of Colorado pot seized on highways increased from an annual average of 2,763 pounds between 2005 and 2008 to an average of 3,690 pounds from 2009 to 2013. The weed was headed for at least 40 different states.

Mark Woodward, a spokesman for the Oklahoma Bureau of Narcotics and Dangerous Drugs, said his organization has seen at least a dozen cases of highly potent marijuana from Colorado entering his state. Before Colorado legalized the drug at the end of 2012, Oklahoma had never recorded a single case of high-grade pot trafficking from its neighbor.

In western Nebraska’s Scotts Bluff County, Sheriff Mark Overman said Colorado marijuana is extra strong, making it more valuable in his region and giving sellers a greater financial incentive to do business there.

“I think this is overdue, and I think other states should jump on board,” Overman said of the lawsuit. “I’m very frustrated. I take an oath of office, as does every other police officer in this country. I don’t just get to pick and choose which laws I enforce.”

Although organizations like the International Association of Chiefs of Police and the National Sheriffs’ Association have warned against legalizing marijuana, the legalization movement also has high-profile law-enforcement supporters. Washington state’s legalization was supported by the sheriff of Kings County, which includes Seattle, as well as two former U.S. attorneys there and the former head of its FBI office.

Inga Fryklund, a former Cook County, Illinois, prosecutor who is a member of Law Enforcement Against Prohibition, a pro-legalization group, said that many rank-and-file police officers and prosecutors secretly support marijuana reform.

“A lot of their time is taken up with stupid drug arrests,” she said.

But she acknowledged deep-seated resistance in law enforcement because people there see marijuana as destabilizing.

“You have to step back a bit and say ‘This is very much like Prohibition of alcohol. All the violence and corruption is there because the stuff’s illegal,’” Fryklund said. She also noted that police agencies are increasingly funded by seizing assets of people accused of drug crimes.

Darrel Stephens, who heads the Major City Police Chiefs Association, said that law enforcement believes legitimate concerns about marijuana legalization have been drowned out by deep-pocketed donors who have funded pro-marijuana ballot measures. At this point, he believes complete legalization is inevitable.

Associated Press writers Grant Schulte in Lincoln, Nebraska, and Tim Talley in Oklahoma City contributed to this report.