As we’ve long suspected, fentanyl is killing more people than heroin, according to a new report from the National Vital Statistics System (NVSS). Does this mean that our drug-taking citizens have developed a taste for a new drug that gives a more powerful high? No, those deaths are a direct result of drug prohibition, and the numbers will continue to go up until we realize, once again, that prohibition doesn’t work.

Everyone knows that prohibition means drugs will often be adulterated, but prohibition also makes drugs stronger. Before alcohol Prohibition, beer and wine were the most popular drinks. After Prohibition, however, the cost of beer increased by more than 700 percent while the cost of high-potency spirits increased by only 270 percent. Smugglers and bootleggers preferred high-potency spirits because they are easier to transport illicitly. Consequently, distilled alcohol and fortified wines became almost 90 percent of alcohol consumption after Prohibition, compared to 40 percent before.

This is known as the iron law of prohibition. When drug traffickers fear getting caught, they prefer the highest potency version of a drug. During alcohol Prohibition, speakeasies were essentially bars that only served Everclear, but that didn’t mean Everclear was actually the most in demand. And, sure enough, after Prohibition ended, people quickly returned to low-potency beer and wine.

The introduction of fentanyl to our drug markets demonstrates the iron law of prohibition at its most dangerous. Fentanyl is a synthetic opioid that is 50 to 100 times stronger than heroin, and it’s significantly more dangerous than traditional poisons like arsenic. A lethal dose of fentanyl is between 2 and 3 milligrams, compared to 100–300 milligrams for arsenic. There are 300–500 lethal doses in just one gram of fentanyl.

That potency is useful for drug smugglers but dangerous to users. Fentanyl’s potency means hundreds of doses can be smuggled in the tiniest crevices of envelopes, packages, and shipping containers, and neither sufficient manpower nor adequate technology exists to stop it. As can be seen in the NVSS report, fentanyl began flooding the drug market in about 2014. In 2011, oxycodone was the No. 1 killer with 5,587 deaths. Fentanyl was 10th with 1,662. Then the government started cracking down on prescription opioids, and people started dying of fentanyl overdoses in shockingly large numbers. By 2014, fentanyl killed 4,223, which moved it into fifth place, but just two years later it was No. 1, with an astounding 18,335 deaths in 2016. In 2017, there were 28,466 deaths from fentanyl or similar synthetic opioids.

Many addicts and drug users, if not most, don’t want fentanyl and are actively trying to avoid it. That can be very difficult when much of street-purchased heroin is contaminated with fentanyl. In one qualitative study of users in Rhode Island, “Nearly every regular heroin user who claimed to have personal experience using illicit fentanyl or fentanyl-contaminated heroin reported a strong dislike for its effects.” One addict said his willingness to use fentanyl-contaminated heroin depends on “the availability of other batches and how sick I am. If I’m sick, I gotta do it, you know?” But he knows he has to be cautious, “I’ll do a little pinch and I’ll figure it out from there, but I won’t start big.”

Other addicts try to find prescription opioids, but recent and ongoing crackdowns on medical prescriptions and opioid production have made them harder to find. “I used to take just the pills,” said one addict, “and then I started doing dope, the heroin, only when I could get it, when it was cheaper. But I don’t prefer it because you never know what you’re getting. It’s scary, so I’m more into pills.”

Some studies have shown that some users seem to prefer fentanyl, or at least don’t mind it. This is likely true, just as there were drinkers who preferred hard spirits both during and after Prohibition. Nevertheless, due to the nature of black markets, we don’t really know what the demand for fentanyl would be in a legal or decriminalized market. We can confidently say, however, that users certainly want to know if their heroin is tainted by a potentially lethal drug.

Recently, some major “dark web” drug suppliers voluntarily banned sales of fentanyl on their platforms, regarding it as too dangerous to their customers and too likely to elicit the attention of law enforcement. Similarly, users in the Rhode Island study sought to avoid fentanyl by relying on trusted dealers.

While such private actions can help, the only thing that will really mitigate fentanyl deaths is drug decriminalization or legalization. And, if you think fentanyl is bad, carfentanil, a large animal tranquilizer that is 100 times more potent than fentanyl, has begun showing up on the streets and killing people. The iron law of prohibition continues to work its deadly logic.