Andrew Yang said if he's elected president he'll legalize marijuana and pardon non-violent drug offenders on April 20, 2021.

Traditionally, April 20 is a holiday for marijuana enthusiasts, and is often referred to as "4/20."

"I would legalize marijuana and then I would pardon everyone who's in jail for a nonviolent drug-related offense," Yang said on Wednesday. "I would pardon them on April 20, 2021 and I would high-five them on the way out of jail."

Democratic presidential candidate Andrew Yang pledged to legalize marijuana at the federal level if elected president and pardon all those who've been incarcerated for non-violent, drug-related offenses.

"I would legalize marijuana and then I would pardon everyone who's in jail for a nonviolent drug-related offense," Yang said at the National Action Network conference in New York City on Wednesday. "I would pardon them on April 20, 2021 and I would high-five them on the way out of jail."

April 20, or 4/20, is considered a holiday by marijuana enthusiasts.

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Technically, the president cannot legalize marijuana at the federal level without the support of Congress.

However, the president can direct the attorney general to reclassify marijuana from its current classification as a Schedule I drug under the Controlled Substances Act, reserved for drugs with "no currently accepted medical use and a high potential for abuse." Other drugs classified as Schedule 1 include ecstasy and heroin.

The US has the highest incarceration rate in the world and also has the highest overall number of people behind bars. There are approximately 2.3 million people behind bars in the US and roughly half a million are incarcerated for drug offenses — or about one in five people in the system — according to the Prison Policy Initiative.

Read more: Here's where all the 2020 presidential candidates stand on marijuana legalization

In terms of significantly reducing or ending mass incarceration, criminal justice reform advocates often say there's too much focus on non-violent drug offenders given far more people are locked up for violent crimes.

But leniency for non-violent drug offenders is something that's gained bipartisan support in recent years, which was evident in the passage of the First Step Act in 2018.

President Donald Trump signed the act into law late last year. Trump has since called for a new focus on hiring former prisoners to reduce the recidivism rate and high level of unemployment among ex-inmates.

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Meanwhile, a strong majority of US voters support legalizing marijuana at the federal level, which helps explain why nearly all 2020 Democratic candidates — including Yang — support such a policy.

Trump supports decriminalizing marijuana but has said legalization should be left up to states. So far, 10 states and Washington, DC, have legalized recreational marijuana use for adults.