WASHINGTON (Reuters) - U.S. Senate Democratic Leader Chuck Schumer on Friday backed the decriminalization of marijuana, unveiling a bill removing it from the federal schedule of controlled substances days after President Donald Trump softened his own stance over the drug.

People roll a marijuana joint on the informal cannabis holiday, 4/20, corresponding to the numerical figure widely recognized within the cannabis subculture as a symbol for all things marijuana, on the Common in Boston, Massachusetts, U.S., April 20, 2017. REUTERS/Brian Snyder

Schumer said his position had “evolved” and threw his support behind more local efforts to legalize the substance that has already been legalized in some form in most of the 50 U.S. states.

“I have long believed that states should function as their own laboratories of democracy,” Schumer said in a Twitter post.

A Reuters/Ipsos poll conducted last year showed marijuana legalization or decriminalization was popular, especially among young people.

Washington, California, Oregon, Colorado and a number of other states plus the District of Columbia have legalized or decriminalized marijuana for recreational use, while 29 states allow use of marijuana for medical reasons.

It remains illegal, however, under federal law.

U.S. Senator Cory Gardner of Colorado last week said that he had convinced Trump, a fellow Republican, to protect from federal interference those state laws that legalize marijuana for certain uses.

The shift by both Trump and Schumer comes as U.S. Attorney General Jeff Sessions has sought to crack down on marijuana decriminalization efforts.

Sessions, who opposes marijuana use, in January rescinded a policy issued by Trump’s Democratic predecessor, Barack Obama, that dialed back enforcement of the federal ban in states that legalized the drug.

April 20, the date of Schumer’s announcement, is informally celebrated as a holiday by marijuana users known as “4/20.”

Schumer’s new position, first reported by VICE News, comes as Democrats have high hopes to re-take the House and Senate in the November 2018 midterm elections.

“My thinking – as well as the general population’s views – on the issue has evolved,” he said in a statement. “It’s simply the right thing to do.”