On June 25, the US Food and Drug Administration (FDA) approved Epidiolex, a pharmaceutical drug that treats two rare forms of epilepsy with the pot-derived compound cannabidiol (also called CBD). That means the same government that prohibits pot because it supposedly "has no accepted medicinal use" is now officially recognizing a medical use for pot.

You probably already know that pot can be a powerful medicine. You live in a state that recognized the medical value of weed more than two decades ago. But now, for the first time, the FDA has agreed.

That's a momentous change, according to Daniel Shortt, a Seattle cannabis attorney with Harris Bricken law firm. "I think this is a date that we will look back on," he said, "as a big moment on the lines of California legalizing and Washington and Colorado legalizing cannabis."

The newly approved drug is good news for the thousands of people who suffer from Lennox-Gastaut syndrome and Dravet syndrome, the two forms of epilepsy that Epidiolex is designed to treat.

Both of these conditions start in childhood and are marked by nearly constant, debilitating seizures. Across three randomized, double-blind, placebo-controlled clinical trials, Epidiolex was shown to reduce the amount of seizures patients experienced. Hopefully, it will give these people a shot at a more normal life.

The FDA's approval of CBD as medicine is also giving pot advocates hope that federal prohibition might finally start to unravel. That's because one of the primary criteria of keeping marijuana in its current Schedule I class of drugs—the most dangerous and highly controlled class of drugs according to the Drug Enforcement Administration (DEA)—is that it supposedly has "no currently accepted medical use and a high potential for abuse."

Well, the FDA just blew a hole in that argument. They've declared that pot can have medical efficacy that meets rigorous scientific standards. The FDA also said that Epidiolex had been analyzed for its potential for abuse and deemed safe.

So does that mean federal prohibition is officially ending?

Not likely, according to Shortt. He said it's more likely that the DEA gives a narrow exception for CBD only, moving it to a lower scheduling and keeping the rest of marijuana, including THC (the active compound in pot that is responsible for getting you high), as a Schedule I substance.

Dr. Douglas Throckmorton, deputy director of regulatory programs at the FDA's Center for Drug Evaluation and Research, told reporters on a conference call last week that the DEA is already working on reclassifying CBD.

Melvin Patterson, a spokesperson for the DEA, told me that the agency was studying the issue but he could not give me a time frame for when the DEA would make a decision. "The DEA isn't changing its position right now," Patterson said. "That is something that the DEA is looking into further, and they are going to heed recommendations from the FDA."

Hopefully the DEA speedily heeds the advice of the FDA. After all, the scientifically rigorous testing behind Epidiolex confirms something American doctors have known for well over a hundred years.

In 1851, cannabis was added to the United States Pharmacopeia (an anthology used by doctors to list and describe drugs) for treating a laundry list of symptoms, including "convulsions," a term that was historically used to describe seizures.

Researchers and doctors should have spent the next 160 years perfecting how to use cannabis as medicine, but instead the federal government made this plant and its flowers one of the most illegal substances on earth.

It's about time the FDA finally identified one part of cannabis that clearly shouldn't be illegal. Let's hope this leads to more.