In the most serious legal challenge to date against Colorado's legalization of marijuana, two neighboring states have asked the U.S. Supreme Court to strike down the history-making law. 
 
 Nebraska and Oklahoma filed the lawsuit directly with the nation's highest court on Thursday. The two states argue in the lawsuit that, "the State of Colorado has created a dangerous gap in the federal drug control system." 
 
 "Marijuana flows from this gap into neighboring states, undermining Plaintiff States' own marijuana bans, draining their treasuries, and placing stress on their criminal justice systems," the lawsuit alleges. 
 
 DOCUMENT: Read the lawsuit by Nebraska and Oklahoma. 
 
 Colorado Attorney General John Suthers said in a statement that he will defend the state's legalization of marijuana, saying that the lawsuit is, "without merit." 
 
 "Because neighboring states have expressed concern about Colorado-grown marijuana coming into their states, we are not entirely surprised by this action," Suthers said. "However, it appears the plaintiffs' primary grievance stems from non-enforcement of federal laws regarding marijuana, as opposed to choices made by the voters of Colorado." 
 
 Colorado voters in 2012 passed Amendment 64, which legalized use and limited possession of marijuana by anyone over 21. The new law, tied for the first in the nation to widely legalize marijuana at the state level, came after more than a decade of legal use and possession of marijuana in Colorado for certain medical purposes. 
 
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 Stores able to sell up to an ounce of marijuana to any adult with a Colorado I.D. — or a quarter ounce to any adult with an out-of-state I.D. — opened on Jan. 1 this year. So far, recreational marijuana stores in Colorado have made more than $300 million in sales in 2014. The lawsuit does not target Colorado's separate medical marijuana system, where registered patients must be Colorado residents. 
 
 Nebraska and Oklahoma's complaint argues that Colorado does not have authority to pass laws that conflict with the federal prohibition on marijuana. Doing so, the states claim, violates the Supremacy Clause of the U.S. Constitution. 
 
 "Colorado Amendment 64 obstructs a number of the specific goals which Congress sought to achieve," the lawsuit states. 
 
 But much of the complaint focuses on harms the two states say have come to them as a result of legal pot sales in Colorado. The lawsuit says the states have suffered increased costs from arrests, the impoundment of vehicles, the seizure of contraband, the transfer of prisoners, and other problems associated with marijuana — which is strictly illegal in the two states — flowing into Nebraska and Oklahoma. The states say the problems amount to "irreparable injury." 
 
 Supporters erupt in cheers at the passage of Amendment 64. Supporters of Amendment 64, the campaign to regulate marijuana like alcohol, gather at Casselman's in Denver on Tuesday, Nov. 6, 2012. Kathryn Scott Osler, The Denver Post (THE DENVER POST | Kathryn Scott Osler) 
 
 The lawsuit does not cite any figures to back up the claims. 
 
 News stories since Amendment 64's passage have repeatedly noted the complaints of law enforcement officers in neighboring states that marijuana legalization in Colorado is straining their budgets. For instance, the police chief in Sydney, Neb., told a television station this year that half of his department's traffic stops now result in a marijuana arrest. He said the department burned through its yearly overtime budget in six months, mostly paying officers overtime to go to court to testify in marijuana prosecutions. 
 
 A cannabis plant at Northern Lights grow facility in Denver, Colorado on March 27, 2014. (Seth McConnell, Denver Post file photo) 
 
 Another Nebraska television station reported this year that, while the state's highway patrol has not seen a jump in marijuana citations, it seized nearly twice as much suspected drug money in 2014 as in 2013. Late last year, a spokesman for Oklahoma's Bureau of Narcotics and Dangerous Drugs told The Denver Post that Colorado marijuana has earned a reputation for potency in his state. 
 
 The lawsuit argues that Colorado also has done little to keep pot from leaving the state. Marijuana customers are not subject to criminal background checks and their purchases are not tracked, the lawsuit notes. 
 
 "Nebraska taxpayers have to bear the cost," Nebraska Attorney General Jon Bruning said at a news conference Thursday, in comments reported by the Omaha World-Herald. "We can't afford to divert resources to deal with Colorado's problem." 
 
 "Fundamentally," Oklahoma Attorney General Scott Pruitt said in a statement, "Oklahoma and states surrounding Colorado are being impacted by Colorado's decision to legalize and promote the commercialization of marijuana which has injured Oklahoma's ability to enforce our state's policies against marijuana." 
 
 It is unclear whether additional states will join the lawsuit, which could have implications for more than a dozen other states across the country with recreational or medical marijuana laws, as well as those states' neighbors. A spokeswoman for the Kansas attorney general's office said the state is "assessing our options." Meanwhile, the attorney general in Washington state, which also in 2012 legalized marijuana for adults, stood by Colorado. Attorney General Bob Ferguson said in a statement that he would, "vigorously oppose any effort by other states to interfere with the will of Washington voters." 
 
 Colorado Gov. John Hickenlooper earlier this year proposed hiring two analysts to track out-of-state marijuana diversion, something that ultimately wasn't funded. In an interview Thursday, Hickenlooper said he has talked with officials from Nebraska and Oklahoma about their concerns and how to address them. 
 
 "I'm not sure filing a lawsuit is the most constructive way to find a solution to whatever issues there are," he said. 
 
 Legal analysts also expressed skepticism about the lawsuit. 
 
 "Congress can't force states to criminalize marijuana," Vanderbilt law professor Robert Mikos, an expert on the intersection of federal power and state marijuana laws, wrote in a blog post. Oklahoma and Nebraska "cannot simply force Colorado join their fight," Mikos wrote. 
 
 University of Denver law professor Sam Kamin wrote in an e-mail that the lawsuit does not mount much of a challenge to Colorado's ability to legalize marijuana use or possession. Rather, it focuses mostly on the commercial sale and state regulation of pot — meaning, even if it is successful, it might not entirely strike down Amendment 64 but could lead marijuana stores to close. 
 
 Brian Vicente, an attorney who was one of Amendment 64's chief proponents, charged that the lawsuit is "largely without merit." 
 
 Likewise, other legalization advocates blasted the lawsuit. Mike Elliott of the Marijuana Industry Group said the lawsuit, if successful, could lead to a resurgent marijuana black market. Mason Tvert, another of Amendment 64's proponents, said Nebraska and Oklahoma are "on the wrong side of history." 
 
 "It's unfortunate the state of Nebraska is trying to dictate the laws here in Colorado," Tvert said. 
 
 TWITTER: See reaction to the lawsuit on Twitter. 
 
 But groups opposed to legalization cheered the lawsuit. Mark de Bernardo, the executive director of the Institute for a Drug-Free Workplace, said state marijuana legalization violates not only the U.S. constitution but also international treaties to which the United States is bound. Kevin Sabet, a co-founder of the national group Smart Approaches to Marijuana, said legalization of marijuana "is not implemented in a vacuum." 
 
 "Colorado's decisions regarding marijuana are not without consequences to neighboring states, and indeed all Americans," Sabet wrote in a statement. 
 
 John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold 
 
 Staff reporters John Frank and Jesse Paul contributed to this report. ||||| DENVER (AP) — Marijuana is a political debate, not a legal one — for now. 
 
 The U.S. Supreme Court announced Monday that it won't consider a lawsuit filed by two other states challenging Colorado's pot law. But lawyers say that Nebraska and Oklahoma officials could pursue other legal challenges down the road. 
 
 For now, the many states considering pot laws this year won't have immediate guidance from the nation's high court about whether they're free to flout federal drug law by regulating the drug. 
 
 Instead, the 26 states and Washington, D.C., that allow marijuana for medical or recreational purposes don't have any immediate roadblocks on their marijuana laws. 
 
 Nebraska's attorney general said Monday that his state would consider trying again to challenge Colorado's pot law, just not directly to the nation's highest court. 
 
 "What it basically tells us is to go forth in the federal district court to start off the lawsuit," Nebraska Attorney General Doug Peterson said. 
 
 A lawsuit by some Nebraska and Kansas law enforcement officials was dismissed last month by a federal court in Denver. 
 
 "It doesn't mean that all the legal wrangling is done," said Sam Kamin, a law professor at the University of Denver who studies drug law. 
 
 "It just means that for a case to end up before the Supreme Court before we have a new president is extremely unlikely." 
 
 Marijuana legalization advocates immediately seized on the Supreme Court's announcement as a signal that states are free to legalize marijuana if they wish. 
 
 "States have every right to regulate the cultivation and sale of marijuana, just as Nebraska and Oklahoma have the right to maintain their failed prohibition policies," said Mason Tvert, spokesman for the Marijuana Policy Project. 
 
 "Colorado has done more to control marijuana than just about any other state in the nation. It will continue to set an example for other states that are considering similar laws in legislatures and at the ballot box." 
 
 But Colorado officials weren't so sure. Colorado Attorney General Cynthia Coffman, a Republican who opposes legal weed, said that while Nebraska and Oklahoma chose the wrong legal approach, pot is very much a question in need of federal guidance. 
 
 "The legal questions surrounding (marijuana) still require stronger leadership from Washington," Coffman said in a statement Monday. 
 
 There is a pending federal lawsuit challenging Colorado's pot law, though the plaintiffs aren't from Nebraska or Oklahoma. 
 
 Two southern Colorado residents last year sued a neighboring marijuana company, saying the business violates federal drug law and should be blocked. The residents are represented by the Washington-based Safe Streets Alliance, which seeks to have a federal court throw out the state's entire regulated marijuana industry. A Denver District Court hearing in that case has not been scheduled. 
 
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 Associated Press Writer Anna Gronewold in Lincoln, Nebraska, contributed to this report. 
 
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 Kristen Wyatt can be reached at http://www.twitter.com/APkristenwyatt
– While Colorado citizens are taking advantage of their state's marijuana legalization, sheriffs there and in neighboring states are suffering a "crisis of conscience" in upholding that law, according to a suit filed against Colorado today in Denver. Per USA Today, the lead plaintiff, Larimer County Sheriff Justin Smith, calls the case a "constitutional showdown" and says he doesn't know whether to enforce his own state's mandate or the US Constitution (pot's still not legal on a federal level). "[They're] asking every peace officer to violate their oath," Smith says, per USA Today. "What we're being forced to do … makes me ineligible for office." Meanwhile, sheriffs in Kansas and Nebraska who've joined the suit complain that tokers driving back from Colorado are running up overtime bills as police have to handle a significant increase in drug arrests. This isn't the first group to take legal measures against the state. The attorneys general in Nebraska and Oklahoma filed a lawsuit against Colorado last year, saying the free flow of pot across state lines is hurting communities. "Left unchallenged, I am confident Colorado's law will cause long-term harm to Nebraska families," that state's AG, Doug Peterson, wrote in an open letter, as per the LA Times. And two lawsuits filed last month by an anti-drug group express similar complaints and add racketeering charges into the mix, the Huffington Post noted in February. Larimer County's sheriff says the DoJ's mostly hands-off policy in dealing with the new rules amounts to showing folks "how to violate federal law but not get prosecuted," USA Today notes. But a pot advocate says pols and cops should concentrate on more serious crimes. "These guys are on the wrong side of history," he tells the paper.