The District of Columbia legalized recreational marijuana in 2015. Nearly three years later, I still meet people who don’t understand how the law works—sometimes despite living in the city and enjoying cannabis. Almost no one visiting from outside D.C., meanwhile, seems to have any idea what people are and aren’t allowed to do.

If you’re in the nation’s capital and you want to blaze while you’re here, consider this post a loose introduction to our janky grey-market system.

The passage of Initiative 71 in 2014 made it legal under District of Columbia law (but not federal law) for people 21 and older to possess two ounces or less of marijuana, and for people 21 and older to grow up to six cannabis plants in their primary residence. Up to three of these plants can be “mature” at any given time. Initiative 71 also allows adults who are at least 21 to give—as in, for free—up to an ounce of cannabis to another adult who is at least 21. Consumption may take place only in private. No one may use, possess, exchange, or cultivate marijuana on federal property, of which there is quite a bit in D.C.

Under the law, D.C. not only lacks a retail recreational pot system, it forbids even informal pot sales. Individuals cannot sell cannabis to other individuals under any circumstances, nor can they exchange cannabis for other goods and services.

Nonetheless, in the 10 years I’ve lived here, it has never been easier to safely and quickly acquire cannabis from complete strangers. The trick, as several media outlets have recently reported, is that while D.C. residents cannot sell marijuana, they can sell other things for roughly the same price they would charge for marijuana. Then, after the transaction is complete, they can offer marijuana as a free gift to the person who bought the non-marijuana item.

Here’s an example: Last month, some friends and I wanted to blaze after seeing Ron Funches at the DC Improv, so we pulled up the website for Red Eye Delivery, which is like Uber Eats except that it exclusively sells cookies.

I’m not talking about cannabis-infused edibles, here. These are regular ol’ chocolate chip cookies, baked fresh every day from the same ingredients my grandmother used way back when. The difference between her cookies and Red Eye’s cookies is that Red Eye’s cookies cost $60 for a half dozen and you have to be 21 to order them.

An hour later, a delivery driver texted to say he was outside with our chocolate chip snacks. One of us went out, showed our ID, and picked up the order of cookies. After the transaction was completed, the driver presented us with an eighth of marijuana as a gift.

That sounds complicated, doesn’t it?

The law is “as clear as they wanted to make it,” says Joe Tierney, a D.C. resident who runs a guide to the District’s pot scene called “Gentleman Toker.” But it’s still difficult for people to know if they’ve broken city law, or to what extent, until the Metropolitan Police Department (MPD) drops the hammer like it did last weekend, arresting 22 people at a nightclub cannabis event.

“They certainly left up a lot up to interpretation” in terms of what’s allowed and what isn’t, Tierney says. “If you go to talk to Adam Eidinger [a prominent D.C. cannabis activist who spearheaded the push for I-71], he’ll give you one answer, and if you talk to someone at the Metropolitan Police Department, they’ll give another answer. Every lawyer you talk to will tell you something different.”

Tierney maintains a running list of vendors who are “I-71 compliant” on his website, and he suspects all of them have been told by their attorneys that “some version of XYZ is perfectly legal.”

In the first days of legalization, people held the equivalent of swap meets, sharing cannabis seeds and flowers. While many such events are now hosted at high-end nightclubs, Tierney says the really early events happened in peoples’ backyards and empty restaurants.

Entrepreneurs who wanted to graduate from pot exchanges to making money tried collecting donations and then giving pot as a gift. The most well-known such company was Kush Gods, the owner of which has spent several years in and out of jail because he didn’t seem to understand that he couldn’t legally demand money in exchange for marijuana.

Since then, ganjapreneurs have gotten more sophisticated. Besides the buy-one-thing-get-another-free system, there are now regular pop-up events across the city at which marijuana is given to people who pay for admission. More is gifted to those who buy crafts and other goods once inside.

But the city has began to crack down on these events, even though technically no one is selling weed. “They’ve kind of made it clear in the past that if you’re going to be really hot and in public, that’s a problem,” Tierney says.

The MPG has started conducting raids and arrests on the grounds that people are exceeding the legal possession limits. Officers have also objected to people exchanging non-flower products, though it isn’t exactly clear in the law that edibles and concentrates are illegal.

“The cops are not giving us any real information to work with,” Tierney says. “They can just say, ‘This is the law, and we’re going to interpret in the strictest way possible.'”

Not knowing whether your interpretation of the law will get you arrested is an obvious con. Having to sell stuff other than marijuana in order to actually sell marijuana is another. But Tierney also points out that the city is likely losing serious money because of this system.

“There’s this path that’s opened up to the middle class,” Tierney says. “The city can’t see how much money we’re making off this, but there are roughly over 300 brands in the D.C. market.” He believes the vast majority of those businesses are owned by women and African Americans, and that the city should make it easy for people to practice normal, regulated entrepreneurship. (In addition to legalizing possession, sharing, and home growing, Initiative 71 tasked the D.C. government with designing and implementing a tax-and-regulate system, but House Republicans effectively blocked the latter portion of the bill in December 2014.)

For consumers, the fact that you can’t walk into a retail location and buy weed like you would any other legal good probably seems like the biggest hassle. But ever since the rise of the I-71 compliant vendor, my biggest fear has been getting ripped off. What if I buy your cupcake for $60 and then all I get is the cupcake?

“I have heard of some rare occasions where vendors show you one thing and give you something else, but generally everyone is aboveboard because there’s crazy competition,” Tierney says. “You can’t stay in business if you’re not on point.”