It's a fast food innovation that could give new meaning to "special sauce."

Burger chain Carl's Jr. announced Wednesday that it will offer burgers infused with cannabidiol (CBD) oil at one Denver, Colorado, location on April 20. The special "Rocky Mountain High: Cheese Burger Delight" will cost $4.20, natch.

The burgers won't actually contain any CBD, CNBC reports, but about 5 milligrams of the cannabis-derived oil will be mixed into a special version of Carl's Jr.'s "Santa Fe Sauce" that tops the burger (along with jalapenos and pepper jack cheese).

Still, those CBD-sauced burgers are technically a violation of Food and Drug Administration (FDA) rules that prohibit the mixing of cannabis-derived products like CBD oil with food or drink. But they are yet another sign that the CBD fad is overwhelming prohibitionist policies—at least in places where CBD is legal at the state level.

Unlike tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, CBD does not get you "high," but it can anxiety. It's legal in many states where marijuana remains illegal, can be readily purchased online or in retail stores (including some pharmacies), and has attracted the interest of pharmaceutical companies—although its usefulness as a treatment for just about everything remains subject to debate.

Legally, CBD remains in a bit of limbo, too. In last year's Farm Bill, Congress legalized hemp and other cannabis-derived products, like CBD, that contain less than 0.3 percent THC by weight. But that hasn't stopped state-level enforcement efforts, like the raid by state troopers in Ohio, who seized 55 gallons of CBD oil from a truck on Interstate 70 in February; or the local cops in a Dallas suburb who raided a tobacco shop in March and seized "hundreds of pounds of CBD oil in various forms." Regulators in California and elsewhere have targeted bars serving CBD-infused cocktails.

Carl's Jr. 4/20 burger deal is mostly an attempt to score free advertising—because how often is Reason going to write about a fast food chain otherwise?—rather than changing state and federal drug policy. But the two things aren't mutually exclusive. The National Restaurant Association has named "CBD-infused foods" as the top food trend of 2019, and the ongoing mainstreaming of cannabis will make it more difficult for prohibitionists to rationalize such raids. It's one thing for cops to claim that a small tobacco shop was selling a dangerous product, but much more difficult to make the case that a national fast-food chain is endangering the public in the same way.