Time Magazine reports that the DEA is cracking down on synthetic drug dealers. Thus far, more than 150 suspects have been put into custody and over $20 million in cash and assets have been seized. Meanwhile, teenagers are using more and more synthetic marijuana—otherwise known as “K2” or “Spice.” According to the National Institute of Drug Abuse, 11.3% of high school seniors have used synthetic marijuana (the only more-popular drug is natural marijuana).

It’s no secret that synthetic marijuana has a whole host of negative side effects. In fact, LiveScience reports: “There have been an increasing number of cases of people experiencing seizures, heart palpitations, fever, dehydration and some psychotic episodes after using the drug.” They conclude that synthetic pot is far more dangerous than “the real thing.”

So if synthetic cannabis is so much worse than marijuana, why has it grown so much in popularity since its introduction in 2004?

It’s all about legality.

The legality of something flags whether or not the government has deemed it “safe.” If a drug is illegal, kids learn about it in health classes, it becomes stigmatized, and few efforts are made to promote safe usage. Unlike the rebellious teens of the 60’s and 70’s, today’s youth are far more inclined to follow the rules—as evidenced in teen drug use (except for synthetic and natural cannabis) falling across the board. More teenagers think that marijuana is safe, largely because of legalization efforts. It’s not so big a jump to think that synthetic pot must be even safer; it has the “guarantee” of modern science and tech, after all, and can’t be much worse than the real thing.

Various government agencies have tried again and again to make synthetic marijuana illegal. It wasn’t until 2010 when states started to crack down on the substance. But the tough question is: What, exactly, is illegal? For example, Spice, a synthetic marijuana manufacturer, changed its ingredients to comply with DEA and several state standards. The change in recipe has made the law difficult to enforce. Synthetic marijuana remains legal, in some form, in many states.

My guess is that most consumers don’t care about why the drug is legal or illegal. Most users are worried about drug tests and their personal safety. And since synthetic marijuana rarely shows up on drug tests and it’s largely easy to obtain, many will continue to use it.

There’s another factor at play. Remember: Over a third of high school seniors have tried natural marijuana, which is (in my humble opinion) largely safer than alcohol and can be consumed responsibly. For the most risk-averse teens, the jump to an illegal substance might be too much. But since marijuana is socially acceptable, synthetics are just as widely accepted.

The bottom line is that synthetic marijuana can’t be stopped. Companies, recognizing the demand for legal marijuana, continue to innovate to get around the law. Instead, states should legalize natural marijuana so that teens (and adults!) can discover what works better for them. My guess is that if synthetic marijuana had to compete legally with natural marijuana, it would lose out—and quickly.