The Obama administration and many congressional Republicans have been loath to go anywhere near the experiment with marijuana legalization in Colorado and other states. But pressure is mounting on Washington to take a stand on pot, and perhaps soon.

In a lawsuit filed last month with the U.S. Supreme Court, attorneys general of Nebraska and Oklahoma argue that Colorado’s marijuana initiative is spilling over into their neighboring, more conservative states. Marijuana arrests and prosecutions are up over the past year, they say, straining law enforcement budgets as more overtime is paid to handle the uptick in activity. And drugged driving is a growing problem, they contend.


But the neighbor states are also taking aim at a federal government that seems highly reluctant to tackle the issue. And with several more states considering legalizing recreational marijuana, the Justice Department and Congress may be forced to clarify what’s OK or not when it comes to marijuana, experts say.

“It’s gone from a slow burn to a hot, cauldron bubble,” Douglas Berman, a law professor at Ohio State University, said of tensions over cannabis policy.

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The issue is emerging as a major test for attorney general nominee Loretta Lynch, who will have to decide whether to embrace the hands-off approach to marijuana in the states that the Justice Department has adopted under Eric Holder — or take more decisive action to regulate it.

Experts and advocates floated a range of options if Congress or DOJ were to act, some more far-reaching or politically feasible than others. Anti-legalization advocates want an about-face from the administration: Enforce the existing federal marijuana ban and crack down on legalization regimes in Colorado and elsewhere. That’s a pipe dream for the current White House but not inconceivable if a Republican is elected president in 2016.

Pro-legalization advocates want Congress or the Obama administration to reclassify marijuana under sentencing laws so that it would carry lesser or no criminal penalties. Marijuana is currently considered a “Schedule I” drug, a category that includes heroin and LSD. Even cocaine is deemed less dangerous than pot under federal law.

Other experts say Congress should pass legislation that would deem marijuana federally legal in states that enact legal cannabis laws, thus removing ambiguity in those states. And still others want the administration to establish a standardized regulatory framework throughout the states, as the federal government does with other “vice industries.”

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There are, of course, many issues where the federal government largely cedes authority to the states. But the transfer of legal marijuana across state borders — and the accompanying quality-of-life, crime and budgetary concerns that come with it — provides a more vexing practical challenge than, say, different same-sex marriage laws in the states.

The administration opting not to enforce marijuana prohibition — similar to its decision not to enforce the Defense of Marriage Act before it was overturned by the Supreme Court — has resulted in a legally murky situation where no one is completely sure what states can or can’t do.

The urgency is expected to grow as five states are preparing recreational pot initiatives for the 2016 ballot: Arizona, California, Maine, Massachusetts and Nevada. A trio of other states — Missouri, Montana and Florida — are considering similar ballot measures. Currently, recreational pot is legal in Colorado, Washington state, Alaska and Oregon; an initiative approved by Washington, D.C., voters in November is currently being challenged by some Republicans in Congress.

“I think the next six months to a year is a time that Congress needs to do something relatively big,” Berman said.

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In the suit, Nebraska Attorney General Jon Bruning and Oklahoma Attorney General Scott Pruitt are asking that the high court strike down the commercial elements of Colorado’s marijuana legalization law because the cannabis market infringes on their ability to enforce marijuana laws in their respective states.

In response, multiple experts say, the border states have engaged in “geographic profiling” — singling out vehicles crossing the border from Colorado for suspicion of carrying marijuana. Colorado’s pot industry has created an enforcement nightmare for law enforcement in Cheyenne and Deuel counties in western Nebraska, officials say.

“It’s basically flooded our county,” Deuel County Sheriff Adam Hayward told The Associated Press.

The budgetary issues come as legalization has delivered a tax revenue windfall to Colorado since it took effect a year ago.

The suit calls for the Obama administration to enforce the Controlled Substances Act, which maintains a federal ban on marijuana, in Colorado. So far, Holder and President Barack Obama have mostly declined to do so.

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Colorado Attorney General John Suthers, in a statement after the lawsuit was announced, said his office would “vigorously defend against” the suit, which he said was “without merit.”

Other states that border Colorado — including Utah, Wyoming and New Mexico — have said they are aware of the case but have not signed on. A spokeswoman from the Kansas attorney general’s office told POLITICO that Colorado’s law and the federal government’s limited CSA enforcement “have combined to cause harm in Kansas.”

Many experts consider the suit a long shot to be taken up by the Supreme Court. Even if it were to succeed, it would likely just strip away parts of the law’s regulatory structure — like the institution of stores and dispensaries — while still allowing for personal use and possession. That would only lead to a “Wild West environment” in Colorado and exacerbate the spillover effects in Oklahoma and Nebraska, said Rob Mikos, a professor at Vanderbilt Law School.

Still, the suit has exposed rifts among states over marijuana policy, which have been exacerbated by the Justice Department’s decision to leave states mostly to their own devices on it.

In an August 2013 memo, the Justice Department announced it would not block recreational and medical marijuana in states that had legalization measures. Citing the department’s “limited investigative and prosecutorial resources,” DOJ said it would largely trust states to enforce their own narcotics laws outside of eight select enforcement areas, including sales to minors and drugged driving.

The bordering states’ complaints have drawn notice in Congress. At a hearing last September on the conflict between state and federal marijuana laws, the incoming Senate Judiciary chairman, Republican Chuck Grassley of Iowa, warned that Colorado’s legal pot was moving into other states.

“Is the federal government prepared to pay for the law enforcement costs it is imposing on states like Iowa because it refuses to enforce federal law?” he asked rhetorically. Lynch, the attorney general nominee, is expected to face questions about the issue at her upcoming confirmation hearings.

In many regards, Oklahoma and Nebraska’s lawsuit demonstrates a last-resort tactic for states that don’t see a willing partner in the federal government, but want to try to blunt the rising tide of legal marijuana in the U.S.

But analysts are far from confident that a gridlocked Congress will summon the will to find common ground on such a divisive issue. Though some Republicans and much of the GOP base oppose legalization and would like to see the federal government step up its enforcement, others say more federal action would run counter to the party’s support of states’ rights.

Several polls indicate that a majority of Americans back marijuana legalization. Support is particularly high among young voters — 64 percent of people ages 18 to 34 in a recent Gallup poll said they support pot legalization.

Congress sent something of a mixed signal on marijuana in the $1.1 trillion spending bill passed last month. Anti-legalization hardliners, led by GOP Rep. Andy Harris of Maryland, earned a potential victory by including language that might invalidate D.C.’s Initiative 71. But the bill also included language to prohibit federal agents from raiding medical marijuana facilities in states where pot is legal, codifying the Obama administration’s de facto policy.

Without action from Congress or further clarification from DOJ, friction between the states will only increase, experts say.

“[I]t is a useful reminder that the Constitution recognizes that having states go their own ways is not necessarily an unalloyed good,” said Brannon Denning, a law professor at Samford University. “In some cases, we want there to be a single, national rule governing conduct in all 50 states.”