Man Holding Marijuana Plant Leaves In Hands Getty
Image source: Getty Images.

As we look back at what's transpired in 2016, it could rightly be argued that this was the most successful year ever for marijuana.

2016: Marijuana's most successful year ever

Entering 2016, 23 states had legalized cannabis for medical use, while residents in four states -- Washington, Colorado, Oregon, and Alaska -- had approved the sale of recreational pot to adults ages 21 and up. Furthermore, Gallup's 2015 marijuana poll found that 58% of Americans favored the legalization of recreational weed.

Now, less than two weeks before the end of the year, 28 states have legalized medical cannabis, two of which did so entirely through the legislative process (Ohio and Pennsylvania). The number of recreational pot states has also doubled to eight from four, with residents in California, Maine, Massachusetts, and Nevada all approving statewide initiatives to legalize adult-use weed. Even marijuana's public approval has increased, with the 2016 Gallup poll finding that 60% of Americans want to see pot legal across the U.S. -- a new all-time high. For added context, just 25% of Americans wanted to see marijuana use legalized two decades ago.

The proof of marijuana's success can be seen in its election near-sweep (sorry, Arizona), as well as in the rapidly growing legal dollar figures behind the industry. Investment firm Cowen & Co is forecasting compound annual growth for the legal pot industry of nearly 24% through 2026, while ArcView is calling for 30% annualized legal sales growth through the end of the decade.

Marijuana Cannabis Bud On Top Of Hundred Dollar Bill Getty
Image source: Getty Images.

Marijuana's expansion could very well lead to an employment boom within the industry, with some pundits calling for a 100% to 200% increase in pot jobs available in the near future. CNBC is estimating that the cannabis industry already employs about 150,000 people, so we could be talking about another 150,000 to 300,000 jobs being created solely because of marijuana's state-level expansion.

However, outside the marijuana industry, it could be another story.

A nightmare for employers is brewing

While marijuana's expansion is setting up bountiful opportunities within the pot industry, it could be narrowing employment opportunities elsewhere.

Even though more than half of all U.S. states have legalized medical cannabis, and more than a fifth of the U.S. population will soon have access to legal recreational cannabis following the November elections, the federal government still holds marijuana to be a schedule 1 substance. Schedule 1 drugs are deemed to have no medical benefits and are thus illegal. Employers are within their right to follow federal law during the hiring and/or employment process and administer drug tests that screen for marijuana, even if the state a worker resides in has legalized medical and/or recreational pot. Given that marijuana can stay in a person's system for a considerable amount of time, this could prove a problem for infrequent users in legal states, and especially for medical marijuana patients who need the drug to treat a specific ailment.

As reported by the Los Angeles Times, companies in certain safety-sensitive industries, as well as those that operate directly with the federal government, are unlikely to relax their drug-testing qualifications for initial or continued employment. Industries such as trucking and construction, which require the user to operate heavy machinery, are almost assuredly not going to budge on their marijuana-testing standards, especially with the full effects of marijuana on drivers still not fully known.

Employer Drug Test Marijuana Pot Cannabis Weed Getty
Image source: Getty Images.

Likewise, federal contractor Boeing (NYSE:BA), which employs nearly 162,000 -- many of whom are in Washington and California -- has firmly stated that it has no intention of changing its drug-testing policy regardless of what laws individual states pass. According to the company, "As a federal contractor, The Boeing Company's Drug Free Workplace policy is based on federal standards which define marijuana as an illegal drug. Therefore the use of marijuana by Boeing employees is prohibited." For what it's worth, Boeing hasn't experienced major shifts in hiring despite the passage of recreational marijuana laws in Washington state, but that isn't the case with other industries where it has been difficult to find workers to hire who can pass (and continue to pass) a drug test.

Barry Sample, the aptly named Director of Sciences and Technology for Quest Diagnostics, the company that handles most drug testing for employers, told the Los Angeles Times that most California employers don't plan to change their policies on marijuana, and many of those in Washington and Colorado that had suggested they would alter their drug-testing policies have not followed through.

A reminder of marijuana's many challenges

If there's a lesson to be learned behind the growing clash over legal state-level marijuana use and employers that ardently oppose their employees' use of pot, it's that marijuana's path to success is probably more challenging than most people realize.

Scientist Writing On Clipboard Marijuana Cannabis Getty
Image source: Getty Images.

Until marijuana is rescheduled by the federal government, many employers that are currently testing for it (along with other illegal substances) are probably going to continue to do so. But that's the problem -- the federal government isn't liable to alter its stance on cannabis anytime soon. The U.S. Drug Enforcement Agency had its opportunity to reschedule pot this summer but declined. The DEA cited a lack of safety and medical evidence, as well as a lack of knowledge surrounding the chemical makeup of marijuana, as reasons for declining to reschedule pot. Petitions that call for the DEA to reschedule or de-schedule marijuana can take years to review.

Also, even though President-elect Donald Trump has demonstrated support for medical marijuana, it doesn't mean that Republican leaders in Congress will agree. Of the states that have not legalized medical marijuana, many are led by Republican legislators.

These employment challenges compound a number of existing challenges that actual marijuana businesses are also facing, which stem from the federal government's stance on marijuana. As long as cannabis stays as a schedule 1 substance, access to basic banking services (i.e., checking accounts and lines of credit) will remain constrained, and pot industry businesses probably won't be able to take normal business deductions come tax time.

Though marijuana's expansion could continue in 2017 and beyond, it's expected to be filled with some sizable hiccups and speed bumps. That's more than enough for this Fool to keep his investable money far, far away from this perceived-to-be-high-growth industry, and it should give you a reason to pause as well.

Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.