What happened

Marijuana stocks went on a tear Wednesday, with shares of Aurora Cannabis (NYSE:ACB) rising 9.7%, Aphria (NASDAQ:APHA) going up 9.4%, and industry giant Canopy Growth (NASDAQ:CGC) gaining 5.7% through 12:30 p.m. EST.

You can thank the United Nations for that.

A close-up of marijuana plants

Image source: Getty Images.

So what

Earlier this morning, by a vote of 27 to 25, the United Nations Commission on Narcotic Drugs approved a decision to remove cannabis from Schedule IV of the U.N.'s 1961 Single Convention on Narcotic Drugs. In effect, although cannabis remains "a banned drug for non-medical use under UN law," reports Vice.com, it's now been officially differentiated from more dangerous drugs such as heroin, and it can be legally used as a medical treatment in countries signatory to the treaty.  

Experts are calling the decision "a giant step toward the normalization of cannabis in medicine above all." As Marijuana Business Daily reported today, "countries that basically mirror the U.N. scheduling in their domestic legislation [can be expected to move toward] national descheduling and remove obstacles to use cannabis for medical and research purposes."

Now what

The U.N.'s decision seems to promise an immediate boost for stocks that supply marijuana for medicinal uses -- as do each of Aurora, Canopy, and Aphria. In time, it could even lead to full-scale legalization -- not just in the U.S., but around the world -- and marijuana investors are pretty high on that prospect, too.

Still, before marijuana investors get too excited about this news, here's what you need to know about how U.N. treaties work in practice: Basically, there are two kinds, those that "self-execute" (meaning that their provisions are binding upon countries once they sign the treaty) and those that do not self-execute.

The 1961 Single Convention on Narcotic Drugs, unfortunately, is one of the latter. And that means that, even among countries that have signed the convention, marijuana won't magically become "legal" overnight, even for medicinal purposes. Each country still needs to first write and pass amendments to its laws for this purpose before legalization can happen, and even among treaty signatories, there's no guarantee that they will do that.

Long story short, while today's news is good news for marijuana investors, don't expect it to have any immediate effect on sales, or on profits, for this still deeply unprofitable industry.