The U.S. Is Easing Marijuana Restrictions. Here’s How It Works.

The Biden administration moved on Thursday to downgrade marijuana from the most restrictive category of drugs.

The proposed rule, submitted to the Federal Register, is subject to a 60-day comment period, kicking off a lengthy approval process before it takes effect.

The proposal, which would move marijuana to Schedule III, from Schedule I, signals a significant shift in how the federal government views the substance, even as it does not legalize the drug. Its classification as one of the most dangerous and habit-forming substances has long drawn criticism, and recategorizing the drug is an acknowledgment by the federal government that the drug has some medicinal value and lower potential for abuse.

The categories of controlled substances determine production amounts, access, research and legal consequences. Some experts have argued that cigarettes and alcohol, which are not in any of the five categories of controlled substances, should be included in Schedule I because of their demonstrated high risk of abuse and addiction.

In a recorded video, President Biden praised the step, describing it as “monumental.”

“Far too many lives have been upended because of a failed approach to marijuana, and I’m committed to righting those wrongs,” Mr. Biden said. “You have my word on it.”

Here is a look at the five categories, or schedules, including some of the drugs in each designation. Opioids fall into all five schedules, depending on the exact drug.