Colorado's Illegal Burger doesn't put drugs in the food. That would be illegal under federal law. But it does offer customers a package of emulsified CBD powder to sprinkle over their meal. 

Jim Nixon, CEO of Illegal Burger's parent company, told Cheddar the idea was inspired by his son, Jordan, who suffers from multiple sclerosis.

"Over the years he was taking a lot of shots into the belly, a lot of opiates, a lot of steroids, so his quality of life wasn't all there," Nixon said. 

The steroid injections, in particular, caused Jordan to gain an unhealthy amount of weight and didn't seem to alleviate his symptoms. That changed when he started taking a daily dosage of CBD, Nixon said, which apparently helped regulate his weight, reduce the size of his brain lesions, and stop flare-ups. 

Though clinical research on the effects of CBD is still limited, a growing cottage industry for CBD-infused products is making the case for its wide-ranging health benefits. Some clinical studies have found it may treat anxiety, insomnia, and some forms of chronic pain. 

The success story inspired Nixon to launch his own company selling CBD-infused water and 15-mg packages of CBD powder, which to this day serves as Illegal Burger's unique condiment.

The burger chain considered serving CBD a few years ago, but at the time the law was still ambiguous. Then hemp, from which CBD is derived, was federally legalized in 2018.

Colorado state law allows CBD to be infused into food, but technically the practice is still banned under the Federal Drug Administration. 

For now, Illegal Burger, which plans to expand into Texas in the near future, has decided to play it safe and keep the CBD on the side. This has the added benefit of attracting a wider customer base into the store who may or may not be comfortable with taking the substance. 

"A lot of folks aren't really familiar with CBD, and they can come in have great food and not have to be concerned about whether or not there is CBD in the food," said Rick Grossman, franchise development coordinator for Illegal Burger.