Reclassifying marijuana under federal rules would be a mistake — and isn’t necessary for further medical research.

T oday, Donald Trump will be in Queens to attend the men’s final for the U.S. Open. He’ll have to be luckier than many of the athletes competing in the tennis tournament to avoid the smell of marijuana. City Journal recounts that several of them have complained of a stench comparable to “Snoop Dogg’s living room,” as German tennis star Alexander Zverev put it.

Then again, if the skunky odor of weed mars Trump’s experience of the tournament, perhaps he will have second thoughts about relaxing the federal government’s restrictions on the drug. The Wall Street Journal reported last month that he was considering reclassifying pot as a Schedule III drug. He has yet to take this step. Emerging evidence about the many downsides of the mainstreaming of marijuana argues strongly against his doing so.

Any opposition to further loosening rules about marijuana usage might seem foolish, if you were only going on measures related to its present popularity and prevalence. Recreational marijuana is now legal in 24 states and in Washington, D.C. Medical marijuana is legal in 40 states. There is genuine public sentiment behind this legal regime. Almost 90 percent support some form of marijuana legalization. Even Trump’s own base is divided on the issue.

And people aren’t just talking the talk; they’re taking the toke. Young and old alike: One study found that about 16 percent of twelfth graders had used marijuana in the past 30 days, and that 5 percent were daily users. Another study found that marijuana use by those 65 and older increased by 46 percent from 2021 to 2023; 7 percent of this demographic that year reported taking the drug in the past month.

But this very pervasiveness may be enabling us to see more clearly the dangerous consequences of widespread marijuana use. There is increasing evidence of an association between marijuana use and poor heart health, heart attacks, and cardiovascular death. Marijuana places the brain at risk as well. Studies have now linked marijuana use with suicidal ideation and schizophrenia, especially for young people.

Even those who avoid such dire consequences still have greater difficulty managing the basics of daily life. As Patrick Brown observed in City Journal, users are predisposed to do worse in school and to earn and work less (with drug use now increasingly likely to affect their work performance); they are also less likely to marry.

All the pop culture dismissal of the idea that marijuana is addictive can’t change the reality that 20 percent of users do show some sign of cannabis use disorder. Not even the very young are immune to the cultural externalities. The widespread availability of marijuana edibles has led to a surge of cannabis-related poisoning incidents (from 909 in 2009 to 22,000 last year), some involving children as young as two.

The action Trump is considering would not drastically change the legal status of marijuana. Some criminal penalties would be reduced; others would remain in force. Classifying it as a Schedule III rather than a Schedule I drug would still apply to it the same federal regulations currently in force for such substances as testosterone and ketamine. It would allow more medical research into the drug and enable marijuana businesses to take greater advantage of some of the same provisions of tax law as other businesses. It may be true that, in many states, marijuana is now treated like any other consumer product. But by allowing its purveyors to expand, these further tax advantages would exacerbate the ill effects of marijuana legalization. In many places, that has included continued growth in the black market for marijuana.

There are better steps Trump can take. If he and some among the MAGA base are interested in further medical research, the Trump administration can focus on this without rescheduling, as the Manhattan Institute’s Charles Fain Lehman has argued. It can, for example, work to execute a law Congress has already passed intended for this exact purpose: the Medical Marijuana and Cannabidiol Research Act (MMCREA). Smaller, more targeted steps that simplify medical research would both increase our knowledge about the drug’s effects while not contributing to its further mainstreaming.

At his best, Donald Trump has defied elite-enforced consensus, has resisted the demands of big business, and has supported the vigorous enforcement of public order. Whether a whiff of marijuana mars his visit to the U.S. Open as it has the experience of the competing athletes, Trump could fulfill all three of these imperatives by not whiffing on the chance to stop the transformation of the rest of America into Snoop Dogg’s living room.