Former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE defended his reasoning to not legalize marijuana on a federal level if elected president, saying there is not “enough evidence” as to “whether or not it is a gateway drug.”

Speaking at a town hall in Las Vegas on Saturday, the 2020 Democratic presidential candidate said whether the U.S. should legalize cannabis on a federal level is still up for debate as far as he is concerned.

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“The truth of the matter is, there’s not nearly been enough evidence that has been acquired as to whether or not it is a gateway drug,” Biden said, according to Business Insider. “It’s a debate, and I want a lot more before I legalize it nationally. I want to make sure we know a lot more about the science behind it.”

Biden, as he has throughout his time on the campaign trail, said he supports medical marijuana and insisted possession of the substance "should not be a crime."

But he also said Saturday that he thinks the decision to legalize marijuana should be left up to individual states.

“States should be able to make a judgment to legalize marijuana,” he said at the town hall.

As for legalization on a federal level, Biden said more research is needed.

"It is not irrational to do more scientific investigation to determine, which we have not done significantly enough, whether or not there are any things that relate to whether it's a gateway drug or not," Biden said.

Several of his top Democratic rivals in the race have thrown their support behind legalizing marijuana, which is currently classified as a Schedule I substance, which the Drug Enforcement Administration defines as drugs “with no currently accepted medical use and a high potential for abuse.” Other Schedule I drugs include heroin and LSD.

Biden’s campaign previously noted the former vice president would reschedule the substance as a Schedule II drug to aid in researching its health impacts.

Sens. Cory Booker Cory Anthony BookerThe movement to reform animal agriculture has reached a tipping point Watchdog confirms State Dept. canceled award for journalist who criticized Trump 3 reasons why Biden is misreading the politics of court packing MORE (D-N.J.), Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE (D-Mass.), and Bernie Sanders Bernie SandersSirota reacts to report of harassment, doxing by Harris supporters Republicans not immune to the malady that hobbled Democrats The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election MORE (I-Vt.) have all said they would make marijuana legal on a federal level if elected president.

Democratic presidential candidate Andrew Yang Andrew YangBiden's latest small business outreach is just ... awful Doctor who allegedly assaulted Evelyn Yang arrested on federal charges The Hill's Campaign Report: Biden weighs in on police shootings | Who's moderating the debates | Trump trails in post-convention polls MORE in a tweet Monday morning said he believes marijuana should be legal throughout the country, a position he has held since releasing a plan that would pardon individuals who are imprisoned for nonviolent marijuana convictions.

Marijuana should be legal nationwide. It is already legal in several states, it reflects a safer approach to pain relief than opiates, and our administration of drug laws is deeply uneven and racist. https://t.co/0Uhl17MW98 — Andrew Yang (@AndrewYang) November 18, 2019

--This report was updated on Nov. 18 at 11:16 a.m.