WASHINGTON — The federal government would be forced to respect state laws on marijuana under a bill introduced Thursday by U.S. Sens. Cory Gardner and Elizabeth Warren.

The measure, which is welcomed by the cannabis industry but faces a tough path to becoming law, wouldn’t legalize the drug in states that haven’t sanctioned its use or sale. Nor would it expand its legality beyond whatever a state already has approved — say, to authorize recreational use in a state that has approved marijuana only for medical purposes.

But in states that have welcomed marijuana, including Colorado, the measure would end the current conflict between federal and state law by giving states the upper hand.

“We just want the federal government to get out of the way,” Warren said.

Removing the state-federal conflict is especially important for the business side of the cannabis industry. Because marijuana is illegal at the federal level, cannabis companies face a number of financial obstacles — the biggest being their inability to use banks or bank services.

“That forces a multibillion industry to operate all in cash,” Warren said. “That’s bad for business and bad for safety.”

The Gardner-Warren bill would lift that restriction.

“It’s time that we take this industry out of the shadows,” said Gardner, a Republican from Colorado.

Still, there would be limitations. For example, the sale of marijuana would be prohibited at rest areas and truck stops, according to a bill summary.

Forty-six U.S. states and several territories have legalized cannabis in some fashion. Some allow cannabidiol, or CBD, products for specific health conditions; others have medical marijuana programs; and 10 permit recreational cannabis use.

Whether this state-level popularity translates to a change in federal law remains to be seen.

While the odd-couple alliance of Gardner and Warren, a Democrat from Massachusetts, is notable, their combined efforts still may not be enough to get the proposal through Congress.

Past legislative efforts — on topics such as banking and full-fledged legalization — have been stymied or stalled. One small victory for cannabis advocates in Congress has been recent prohibitions on U.S. Justice Department interference in state-legalized medical marijuana programs.

Gardner said his and Warren’s bill — the Strengthening the Tenth Amendment Through Entrusting States Act, or STATES Act — already had at least four co-sponsors on the Senate side, but he admitted there was a “significant education push we have to do” to garner more support.

At the very least, however, the bill has the support of Gardner’s fellow Coloradan and Senate Democrat Michael Bennet.

“Congress needs to join (the) 21st century on marijuana regulation,” Bennet wrote in a Twitter post soon after Gardner and Warren made public their legislation.

Joined @SenCoryGardner to introduce STATES Act to provide more certainty to patients, businesses, & consumers in CO. Congress needs to join 21st century on marijuana regulation. This bill even more important since AG Sessions upended the will of our state by rescinding Cole Memo. — Michael Bennet (@SenBennetCO) June 7, 2018

A companion measure in the House also was introduced this week, with U.S. Rep. Jared Polis, D-Boulder, as a co-sponsor.

Reading the congressional tea leaves is never an easy task — especially in this administration, said Robert Mikos, a cannabis policy expert and law professor at the Vanderbilt University Law School.

“It’s a pretty bold step but not as bold or aggressive as (Sen.) Cory Booker’s Marijuana Justice Act,” Mikos said, referencing the New Jersey Democrat’s proposed bill to deschedule marijuana and address racial justice concerns, including prior convictions for low-level drug crimes.

“I think (the Warren-Gardner) has a much better chance of passing than that proposal did,” he added.

Still, the more measured approach might be too modest for its own good, he said.

The STATES Act outlines a few guardrails — notably age limits and sales barred at transportation facilities — but it’s lacking other restrictions and leaving the power at the state level, Mikos said.

“That can be problematic if a state does something unexpected that maybe Congress would not have approved of,” he said.

For Gardner, the current effort represents the latest turn in a roller-coaster relationship that he has had with marijuana and the Trump administration since the start of the year.

Much of the drama started in January, when U.S. Attorney General Jeff Sessions rolled back Obama-era policies that generally left alone states that sanctioned marijuana.

The move prompted Gardner to use Senate rules to block appointments to Justice Department for several weeks. Gardner ultimately lifted those holds after he said he received assurances from President Donald Trump that the Justice Department would back off.

Gardner and Sessions are scheduled to appear at this weekend’s 2018 Western Conservative Summit in Denver.

Regardless of the bill’s chances, its introduction was welcomed by the cannabis industry in Colorado and beyond.

The Marijuana Policy Project, a D.C.-based legalization advocacy organization, hailed the STATES Act as “the most significant piece of marijuana-related legislation ever introduced in Congress.”

“With its bipartisan backing in the Senate, it symbolically signals the eventual end of marijuana prohibition at the federal level,” Don Murphy, the organization’s conservative outreach director, said in a statement. “This legislation reflects the position President Trump took on marijuana policy during his campaign, and it comes shortly on the heels of the positive comments he made to Sen. Gardner.

“The president has a unique opportunity to get behind historic legislation that enjoys solid support on both sides of the political spectrum.”

A Quinnipiac University poll released in April showed that 74 percent of American voters surveyed indicated support for legislation that shielded legal marijuana states from federal interference or intervention.

Not all are on board with the approach.

Anti-legalization organization Smart Approaches to Marijuana chastised the senators, stating the bill would fuel an “addiction-for-profit” industry.

“While Sen. Gardner is calling this a ‘states’ rights’ approach, this bill essentially amounts to the federal legalization of marijuana,” said Kevin Sabet, president of Smart Approaches to Marijuana. “The bill would shield the pot industry in states that have liberalized their drug policies and prevent the enforcement of federal law.”