President Donald Trump signed an executive order moving marijuana from a Schedule I to a Schedule III controlled substance, despite many Republican lawmakers urging him not to.

“I want to emphasize that the order I am about to sign is not the legalization [of] marijuana in any way, shape, or form – and in no way sanctions its use as a recreational drug,” Trump said. “It’s never safe to use powerful controlled substances in recreational manners, especially in this case.”

“Young Americans are especially at risk, so unless a drug is recommended by a doctor for medical reasons, just don’t do it,” he added. “At the same time, the facts compel the federal government to recognize that marijuana can be legitimate in terms of medical applications when carefully administered.”

Under the Controlled Substances Act, Schedule I drugs are defined as having a high potential for abuse and no accepted medical use. Schedule III drugs – such as anabolic steroids, ketamine, and testosterone – are defined as having a moderate potential for abuse and accepted medical uses.

Although marijuana is still illegal at the federal level, 24 states and the District of Columbia have fully legalized marijuana within their borders, while 13 other states allow for medical marijuana.

Advocates for easing marijuana restrictions argue it will accelerate scientific research on the drug and allow the commercial marijuana industry to boom. Now that marijuana is no longer a Schedule I drug, businesses will claim an estimated $2.3 billion in tax breaks.

Chair of The Marijuana Policy Project Betty Aldworth said the reclassification “marks a symbolic victory and a recalibration of decades of federal misclassification.”

“Cannabis regulation is not a fringe experiment – it is a $38 billion economic engine operating under state-legal frameworks in nearly half of the country that has delivered overall positive social, educational, medical, and economic benefits, including correlation with reductions in youth use in states where it’s legal,” Aldworth said.

Opponents of the reclassification, including 22 Republican senators who sent Trump a warning letter Wednesday, point out the negative health impact of marijuana use and its effects on occupational and road safety.

“The only winners from rescheduling will be bad actors such as Communist China, while Americans will be left paying the bill. Marijuana continues to fit the definition of a Schedule I drug due to its high potential for abuse and its lack of an FDA-approved use,” the lawmakers wrote. “We cannot reindustrialize America if we encourage marijuana use.”

Marijuana usage is linked to mental disorders like depression, suicidal ideation, and psychotic episodes; impairs driving and athletic performance; and can cause permanent IQ loss when used at a young age, according to the Substance Abuse and Mental Health Administration.

Additionally, research shows that “people who use marijuana are more likely to have relationship problems, worse educational outcomes, lower career achievement, and reduced life satisfaction,” SAMHA says.