Chances are that if you look around, you'd struggle to find stocks that, as a group, have performed better over the trailing year than marijuana stocks. A majority of those with market caps in excess of $200 million have shot higher by more than 100%, with some pushing through even larger trailing-year gains. And if we look at the macro trends behind this move, it's not hard to see why investors are so excited.

To begin with, we've witnessed a discernible shift in the way the public thinks about marijuana. In the mid-1990s, before cannabis was first legalized by California for compassionate medicinal use in 1996, just a quarter of those surveyed by Gallup wanted to see pot legal across the country. As of its 2016 survey, this figure had jumped to 60%, which is an all-time high. Similar favorability was shown in an April 2017 CBS News survey where 61% of respondents answered that they wanted to see marijuana legalized nationally. Such strong support suggests lawmakers will have to adapt their views to that of the public's, or risk being voted out of office.

A person holding a cannabis leaf amid a field of cannabis plants.

Image source: Getty Images.

Legal sales growth has been another major source of investor inspiration. A report released this year by Marijuana Business Daily, entitled "Marijuana Business Factbook 2017," showed that U.S. legal sales are on track to grow by about 30% in 2017 to a range of $5.1 billion to $6.1 billion, and 300% overall between 2016 and 2021 to approximately $17 billion. The simple assumption is that investors expect this legal sales growth to translate into top- and bottom-line growth for marijuana stocks.

The weed industry faces challenges galore

Yet, in spite of these big gains, we've also seen that pot stocks are up against an exceptionally challenging environment. At the federal level, marijuana is still a Schedule I drug, which means it's entirely illicit, and on par with drugs like LSD and heroin.

It also means that marijuana businesses face a slew of disadvantages. These include the inability to take corporate income-tax deductions like normal businesses, since IRS tax code 280E disallows deductions for businesses that sell federally illegal substances, and little or no access to basic financial services. Banks and credit unions typically report to the Federal Deposit Insurance Corporation (FDIC), and since the FDIC is a federally created entity, financial institutions fear criminal charges and/or fines from offering services to marijuana-based businesses.

A book on state and federal marijuana laws next to a judge's gavel.

Image source: Getty Images.

Another issue with the current federal regulation is that it creates a Catch-22 for the medical side of the equation. Lawmakers want more clinical evidence that compares medical cannabis' risks and benefits before they'll consider rescheduling or descheduling the drug. Unfortunately, its restrictive scheduling makes running sanctioned clinical studies almost impossible at times, putting clinical research at a standstill.

Has the NFL had a change of heart on medical marijuana?

However, all it might take is for one prominent name, or organization in this instance, to change that.

As reported earlier this month by The Washington Post, the National Football League (NFL) has written to the NFL Players Association (NFLPA) to offer to work together to study the possible uses of medical marijuana as a pain management tool for both acute and chronic conditions. The NFLPA is already running a study examining the effects of marijuana on the health and safety of its players, and per the Post has yet to respond to the NFL's offer for assistance.

DeMaurice Smith, the NFLPA's executive director had this to say: "I do think that issues of addressing it [cannabis] more in a treatment and less punitive measure is appropriate. I think it's important to look at whether there are addiction issues. And I think it's important to not simply assume recreation is the reason it's being used."

A football laying on a field in the foreground with football players huddling in the background.

Image source: Getty Images.

The NFL has had a long-standing policy of coming down harshly on players caught using a banned substance, of which marijuana is included. The idea that it's at least exploring the idea that medical marijuana may offer benefits to its players is a major deviation from its previous norm.

What's more, the NFL is the most popular sport in the U.S., with 33% of respondents in a Harris poll in 2015 labeling pro football as their favorite sport. By comparison, baseball was a distant second with 15%, and men's college football came in third with 10% of the vote. The NFL has massive viewership statistics and plenty of prestige, meaning a change in its policy could actually makes waves with the public and on Capitol Hill. That's why this offer by the NFL to the NFLPA to explore medical cannabis research opportunities is such a big deal.

Hold your horses, marijuana stock investors

But before you get too excited and rush to buy marijuana stocks, keep one major fact in mind: The current Republican administration is unlikely to budge on the federal government's current scheduling of pot.

When Gallup conducted its 2016 poll on marijuana, it found that only two groups of people have an unfavorable view on weed: senior citizens and Republicans. On Capitol Hill, Republicans are in control of Congress and the White House, and quite a few are senior citizens, which pretty much dooms any chance of progress during the President Donald Trump's administration.

President Trump signing paperwork, flanked by Attorney General Jeff Sessions and his wife.

Image source: President Donald J. Trump's official Facebook page. Photo by Benjamin D. Applebaum.

Furthermore, Attorney General Jeff Sessions would be sure to put the kibosh on any federal legalization efforts, despite what public opinion shows. Sessions has regularly railed against the idea of legalizing pot, and in May wound up sending a note to Congress requesting that they repeal the Rohrabacher-Farr Amendment, which protects lawfully operating cannabis businesses in legal states. In other words, Sessions would prosecute pot businesses in a heartbeat, if given the chance.

Simply put, a change in sentiment among the public doesn't mean we'll see any changes whatsoever in Washington D.C., and that probably means a continuation of losses for most marijuana stocks.