So far, all the states that have legalized marijuana have done so through grassroots petitions and ballot initiatives meant to bypass risk-averse lawmakers in state houses.

California, Nevada, Maine, Massachusetts, Alaska, Oregon, and the District of Columbia have all followed Colorado and Washington either to legalize the sale and use of recreational marijuana or, at a minimum, to decriminalize possession and consumption of small amounts of the drug.

But 2018 may be a tipping point — the moment when the momentum of pot makes it impossible for state lawmakers to avoid. State legislatures are poised to begin passing marijuana reform laws next year. The taboos against smoking dope may go up in a cloud of narcotic smoke.

Lawmakers must still juggle serious public safety issues, even as they eye what they hope will be new revenue streams from pot that they don't want flowing to neighboring states.

Vermont, Rhode Island, and New Jersey all devoted serious debate to this in 2017, and their state legislatures could send legislation to their governors next year to sign into law.

Vermont is the only state legislature to pass a legalization measure, although Democratic Gov. Phil Scott vetoed it.

With recreational use and sales opening within months in Canada and Massachusetts, neighboring states feel compelled to study and implement new public safety measures. Beyond that, however, lawmakers in these states are also emboldened by polls showing public support for recreational use.

Tom Gorman, director of the Rocky Mountain High Intensity Drug Trafficking Agency, believes 2018 could be a tipping point.

"What I was hoping was the rest of the states would say, ‘OK, we've got Washington, and we've got Colorado, let's wait and see what happens so we can make an informed decision one way or the other," said Gorman, whose Denver-based organization supports federal and local anti-drug policing. "Either it wasn't as bad as the anti-marijuana folks said it was, or, ‘My God, this is disastrous, we don't want this for our state.'"

But Gorman's longtime adversary in the recreational legalization battle, Brian Vicente, an attorney who has been a leader in Colorado's decades-long fight over legalization, thinks otherwise. "I think we've probably cleared the tipping point," he told the Washington Examiner. "I think when California and Massachusetts came on board and legalized — I mean, California's such a massively recognized global economy and Massachusetts, this puritanical, historic state — I think those two for me signaled that it's the beginning of the end for prohibition."

What develops next in pot policy is likely to be shaped by data from the early legalizers, Colorado and Washington, by how it is interpreted, by how legislatures respond to legalization as opposed to citizen ballot initiatives, and by whether the federal government will step in.

If Vermont, Rhode Island, and New Jersey make moves, and even if only one or two other voter-based initiatives passed, fewer states would remain that didn't share border with a state with legal marijuana. Some people thought Colorado and Washington were "experiments" and would remain highly quarantined, but it was an illusion.

Unreliable data

Getting a clear "before and after" picture of the effects of legalized marijuana isn't easy. Some experts have suggested that a comprehensive picture could take 20 years or more to become clear because data can be affected by so many other sociological factors.

"What I hear from Colorado is that, they say, you need to wait a couple years. Because the data sets right now are very immature and we don't really know as much as we'd like to know," said Vermont State Rep. Scott Beck, a Republican.

Beck's concerns about "immature" data are well-founded. For example, one of the first comprehensive studies on the effects of legalization was published by the Colorado Department of Public Safety in March, 2016. It began with a strong caution:

"It is too early to draw any conclusions about the potential effects of marijuana legalization or commercialization on public safety, public health, or youth outcomes, and this may always be difficult due to the lack of historical data. Furthermore, the information presented here should be interpreted with caution. The decreasing social stigma regarding marijuana use could lead individuals to be more likely to report use on surveys and to health workers in emergency department and poison control centers, making marijuana use appear to increase when perhaps is has not.

"Finally, law enforcement officials and prosecuting attorneys continue to struggle with enforcement of the complex and sometimes conflicting marijuana laws that remain. Thus, the lack of pre-commercialization data, the decreasing social stigma, and challenges to law enforcement combine to make it difficult to translate these early findings into definitive statements of outcomes."

Just four months before pot sales began in Colorado, Dr. Larry Wolk became the executive director and chief medical officer for the Colorado Department of Public Health and Environment. Wolk says he's often in contact with officials from other states and other countries, and says the number one piece of advice he gives them is usually the same, and it is about data.

"Conceptually, stop thinking about this as a ‘starting from zero' — you know, if it's not legalized — to some dramatic number as a result of legalization," Wolk said. "So recognizing, what's the base use of marijuana amongst adults and kids.

In Colorado, public safety concerns have broken along two lines: Concerns about the effects on those underage, whether it's direct use by teens or children being born with THC detectable in their systems, and concerns about public safety on the roads, mainly because of people driving while stoned.

Drugged driving

Perhaps nothing has confounded policymakers more than the inability to measure impairment due to marijuana use quickly in the same way a breathalyzer gauges a driver's blood alcohol level, which is a reliable measurement of impairment. Not only does the absence of a similar testing tool make roadside analysis difficult for law enforcement, it also makes studying the issue murky as well.

Complicating those factors is the notion, which many experts say is incorrect, that marijuana "impairment" on driving can be measured like alcohol.

"Peak impairment does not occur when THC concentration in the blood is at or near peak levels," a 2017 report by the National Highway Traffic Safety Administration noted. THC is the active compound in marijuana responsible for its psychoactive effects. "Peak THC level can occur when low impairment is measured, and high impairment can be measured when THC level is low."

A January release by the Colorado Department of Transportation noted that traffic fatalities were up 24 percent since 2014, the first year that recreational pot was legal. But the word "marijuana" never appeared in that release, and officials never singled out any overriding factors for blame. The same release noted that those figures came during a population boom and also said, "The rise in fatalities is part of a national trend. Fatalities are up nationally by about 8 percent."

Beck says legislators in that state have struggled with what to do about drugged driving, absent any test similar to a breathalyzer.

"Now we're basically talking about having officers doing ‘driving under the influence' tests roadside, which is kind of a throwback to the '70s and '80s, ‘walk the line, touch your nose,'" Beck said.

"It's subjective. How's it going to fare in a court of law? How does an officer determine whether it's alcohol, or THC, or some other substance? We have trained many people in the state to be drug recognition experts. But I don't think we have enough of them that people are confident that we can identify all these people."

Especially concerning to Beck is that Vermont will have to deal with an increase in drugged drivers whether or not the state decriminalizes marijuana because tit has drivers on its roads from Massachusetts and Canada, where dope will be legal.

Effects on underage people

Supporters of legalization in Colorado have promoted a pair of studies they say show no increase in teen usage.

The state's "Healthy Kids Colorado" survey polls 17,000 youth. From 2013 to 2015, the percentage of youth who said they had used marijuana once in the last month inched up from 20 percent to 21 percent, and that 21 percent is comparable to the national average.

Even though there was an uptick from 20 to 21 percent over two years, scientists have said this isn't "statistically significant."

"There's some corridor of variability or error when you do any kind of study," Wolk explained, "and so the reason why we say not to make much of the small increase that occurred the one year which then actually was followed by a small decrease is that, that's within the corridor of variability that … researchers say is what's attributed to chance."

The other study on teen use of marijuana showed a similarly small increase, but relied on a much smaller sample.

Opponents of legalization, meanwhile, highlight statistics from a Pueblo-based hospital showing about a third of all babies tested have shown a presence of THC in their systems.

Tom Tancredo served as a congressman from Colorado for five terms, and ran for president in 2008 on a hardline immigration stance. But he lent his name and voice to pro-legalization radio ads in the run-up to the 2012 vote. He says he's lost friends over this and says he would also support legalization again. Nevertheless, he acknowledges that lawmakers must consider secondary effects. Babies born with THC in their systems are a prime example, he says.

"I think that that should be dealt with legally," he told the Washington Examiner. "Because I believe that's child endangerment. And I think people should go to jail for that. Again, I don't care what you do to yourself, as an adult, but I certainly care what you do to those who are not."

Wolk says there is no data that proves that a mother passing THC to her baby is doing more harm, or as much harm, a mother using alcohol or tobacco during pregnancy. The studies are lacking in part because the federal government's labeling marijuana as a "Schedule 1" drug has prevented many labs from getting the strict permissions needed to do marijuana testing.

"We know enough to say there's not a lot in the way of short-term or acute harm if a baby is born to a THC-positive mom, but there's likely the potential that it does affect or impact the developing brain," Wolk said.

"So, obviously, our policy statement based on all available research we have says that pregnant mothers and breast-feeding mothers should not be using marijuana, period."

Taxation and competition

Some state lawmakers in Vermont and Rhode Island who support either decriminalization or retail legalization often suggest that part of the "inevitability" they feel about the issue is something akin to the "domino theory" from the Cold War era. Once a single region "falls," then so do neighboring regions. It sets off a chain reaction that can't be stopped.

There's also a "funding paradox" for states looking at decriminalization as opposed to full-on commercial sales and legalization. If a state decriminalizes pot rather than legalizes it and collects revenue from taxing it, it feels it's missing out on money for road safety and education and prevention programs for youth.

"In general, our state has no taxing capacity left to run our programs, to educate our children," said Republican Vermont State Rep. Heidi Scheuermann. "Even [former] Gov. [Peter] Shumlin said that a number of years ago, and that's still a fact.

"So, if we're going to create new needs, as a result of — whether it's decrim or legalization of marijuana, we're going to have to find some revenue somewhere to do that.

"I don't know if it has to be done all at once, though," she added, noting that she's depending on a study commissioned by the governor to draw conclusions and find solutions.

Other lawmakers appear to be succumbing to the fear of missing out.

"When Massachusetts goes to a tax-and-regulate structure next year, anybody who's interested in accessing marijuana can easily go to Massachusetts," said Rhode Island State Sen. Joshua Miller, referring not only to the way Colorado taxes pot sales, but also oversees virtually every detail regarding cultivation and distribution, which includes tracking every plant grown with its own barcode. "Then it becomes more of, the revenue is either going to be Massachusetts' revenue or Rhode Island's revenue. And those that think it's a good idea or a bad idea have a different reality to also consider."

Miller, a Democrat, compared the potential for new tax revenues through a tax-and-regulate structure to the expansion of state lotteries in the '80s, or casino gambling in the '90s. When neighboring states adopt the new revenue, other states find it hard to resist.

Competitive pressures come back to Colorado. Its pot revenues, such as they are, could deflate as soon as other states legalize. So a state can be left with the costs of marijuana legalization, but see its revenue hopes dashed.

"There's three times as many people in Los Angeles as there are in the state of Colorado. Now that California has legalized marijuana, I do think they're going to be taking the helm in a lot of ways," Vicente said.

Those who have opposed all movements toward new leniency with marijuana say the taxation lure will remain a Faustian bargain.

"There has been some extra [tax] money, no doubt about it," Gorman said. "Where we missed the boat is, what is it costing us, what are the societal costs? And if you look at alcohol and tobacco, and you say ‘highly taxed products,' the taxes only cover about 10 to 12 percent of societal costs, that's probably not a good investment. And we don't know that yet with marijuana. But we will down the road. And if we use illegal drugs as an example, we'd have to say the odds are it's not going to be a good investment for us."

The federal void

All of this state action comes in a broad federal void. Despite Attorney General Jeff Sessions' dislike of liberalizing of marijuana laws, little action has come from the Department of Justice to roll back activities by states.

Sessions sent a letter to Colorado's Democratic Gov. John Hickenlooper in August asking him how the state was responding to a report of increases in traffic deaths, youth consumption, and emergency room visits.

The response came not only from the Colorado governor, but the state's Republican Attorney General Cynthia Coffman (popular in her party for joining a lawsuit against the EPA's Clean Power Plan). She and Hickenlooper vigorously defended the state's marijuana laws, telling Sessions, "When abuses and unintended consequences materialize, the state has acted quickly to address any resulting harms."

Don Murphy, director of conservative outreach for the Marijuana Policy Project, a lobbying organization dedicated to ending marijuana prohibition, says the quick adoption of recreational marijuana by other states is pushing the federal government into a corner.

"The states don't care anymore what the federal government says or doesn't say. And so, they're just moving along doing their own thing," Murphy said.

Elected officials at the federal level seem uninterested in diving into the issue. The Washington Examiner reached out to representatives on Capitol Hill from Rhode Island, Vermont, and Michigan (where a ballot issue could appear in 2018), and none would comment.

Still, the nation will get a clear preview of just how far legal pot may go, and how willing states are to continue to challenge federal laws, when voters cast ballots in New Jersey this November. Voters there will choose a successor to long-time marijuana foe Gov. Chris Christie. The candidates there have drawn a clear distinction between themselves. The Democratic candidate is ready to work on loosening the state's marijuana laws, and the Republican candidate is firmly opposed.

The legislative hurdle appears to be the most comprehensive test for supporters of legalization. If elected representatives and senators in any of these states can find compromise on a bill, and if a governor of a state feels he or she can sign such a bill into law, then supporters of legalization believe the fight against marijuana prohibition will effectively be over.

"We're at the precipice of actually legalizing it, I believe," said New Jersey State Sen. Nicholas Scutari, a leading advocate for adopting a retail structure based on Colorado's. "So, we might as well be at the head of the pack instead of at the rear, like we have been on so many other issues."