Seemingly nothing can stop the momentum behind marijuana lately. As of the end of 2016, 28 states had legalized medical cannabis, and residents in eight states had authorized the sale of recreational, adult-use pot. By comparison, prior to 2012 there were no recreationally legal states, and prior to 1996, not a single state authorized physicians to prescribe marijuana for medicinal purposes.

The public's opinion of cannabis has also changed just as rapidly. Gallup's polling shows that just 25% of respondents approved of the idea of legalizing weed nationally in 1995, compared to 60% in 2016, an all-time high. Data from a more recent survey from the independent Quinnipiac University showed 59% support for nationwide legalization, as opposed to 36% opposition, and a remarkably high 93% approval for the legalization of medical marijuana, compared to just 6% opposition.

Long story short, the American public wants to see marijuana's expansion continue in an orderly fashion at the state level, or in some cases have the federal government completely decriminalize and reschedule the substance.

Jeff Sessions' candid views on marijuana

However, with Attorney General Jeff Sessions at the helm, you can rest assured that marijuana's march over the next four years is going to be an uphill struggle.

While in the Senate, Sessions was regarded as perhaps the most ardent opponent of marijuana. During a drug hearing last April, Sessions was quoted as saying "good people don't smoke marijuana," to aptly sum up his views on the substance. Sessions also blamed higher marijuana-related traffic fatalities as a reason not to support pot, and pointed to the lax policies of the Obama administration for creating these problems.

A little over a week ago, Sessions was at it again, speaking before the National Association of Attorney's General. While you can watch the two-minute video of Sessions speaking to his peers, here are some of the keynotes of his talk:

"My view is that crime does follow drugs. In the 70s and 80s, we saw so many lives destroyed by drug abuse. And I think the drugs today are more powerful, they're more addictive, and they can destroy even more lives. Young people had their lives destroyed. I, as you know, am dubious about marijuana -- as states can pass whatever laws they choose. But, I'm not sure we're going to be a better, healthier nation if we have marijuana being sold at every corner grocery store. I just don't think that's going to be good for us. We'll have to work our way through that. Marijuana is a cure for opiate abuse? Give me a break! This is the kind of argument that's been made out there to just -- almost a desperate attempt to defend the harmlessness of marijuana of even its benefits. I doubt that's true. Maybe science will prove I'm wrong. But at this point in time you and I have a responsibility to use our best judgment, that which we've learned over a period of years, and speak truth as best we can. My best view is that we don't need to be legalizing marijuana."

And there you have it folks -- Attorney General Jeff Sessions remains no fan of the cannabis industry or its expansion.

One thing Sessions may be wrong about

However, he may also be ignoring some telltale data that suggests marijuana is indeed making inroads in reducing deaths related to opioid overdoses.

A trio of authors in October 2014 published a report online in JAMA Internal Medicine that examined the rate of opioid overdose deaths between 1999 and 2010 in all 50 states. The point being to see whether or not opioid overdose death rates declined in states that had legalized medical cannabis. After adjusting for age and other factors, states with medical cannabis laws had a roughly 25% lower mean annual opioid overdose mortality rate than states without a medical marijuana law. What's more, the longer medical cannabis was legal, the stronger the impact on reducing opioid overdose deaths.

A separate study published last year examined all prescriptions from Medicare Part D that were filled between 2010 and 2013 and found that states that had legalized medical cannabis had a reduction in the number of painkiller prescriptions filled. This not only was estimated to have saved $165 million in costs in 2013, but it's perceived to be a safer alternative to treating chronic pain. Previous data has shown that there have been no marijuana overdose-related deaths compared to the more than 15,000 people who die annually from prescription opioid overdoses.

In other words, medical marijuana does appear to offer an alternative to opioid painkillers in certain instances.

But, will it matter?

Unfortunately, even these studies may not matter to the Trump administration, which appears ready to take a much tougher stance on pot than the Obama administration ever did.

During his campaign, President Donald Trump pledged his support behind medical marijuana "100%," and suggested that recreational weed should remain an issue that's dealt with at the state level. In recent weeks, White House press secretary Sean Spicer has suggested otherwise.

While Trump continues to believe that medical marijuana should be available to states that choose to make it an option for physicians to prescribe, Spicer indicated that the federal government could be tougher with the enforcement of recreational pot laws. At this time no one is exactly sure how encompassing the federal government will be with its enforcement, but it clearly has the industry, and investors, on edge.

Sessions' views on marijuana will only further complicate matters. Though he pledged to follow the president's guidelines on pot, Sessions clearly doesn't like marijuana, and it wouldn't be surprising to see his influence be projected on new federal-level enforcement of the recreational pot industry.

Marijuana's growth has been phenomenal up to this point, but it's possible that the industry may not be infallible after all. Investors should be waiting patiently on the sidelines until we get more clarity on the degree to which the Drug Enforcement Agency plans to enforce federal marijuana laws in the weeks and months that lie ahead.