Politicians representing states that have legalised marijuana have lambasted Jeff Sessions for rescinding a hands-off federal approach to cannabis.

An Obama-era directive had essentially let states manage their own burgeoning marijuana marketplaces, promising an easing of raids and other federal enforcement actions as long as states had enacted “strong and effective regulatory systems”.

In reversing that decision, Mr Sessions potentially upended a growing cannabis industry that has seen eight states with a combined population of nearly 67 million people authorise recreational use since 2014 (another 29 states offer medical marijuana.

Elected officials, some of whom who had warned Mr Sessions off of a possible crackdown in recent months, condemned his move and vowed to press ahead. The backlash spanned the political spectrum, with Democrats and Republicans from states with recreational cannabis industries blasting what they called federal infringement.

Colorado Senator Cory Gardner portrayed Mr Sessions’ shift as a betrayal, saying on Twitter that it “directly contradicts what Attorney General Sessions told me prior to his confirmation” and “trampled on the will of the voters in CO and other states”. He threatened political retaliation.

“I am prepared to take all steps necessary, including holding DOJ nominees, until the Attorney General lives up to the commitment he made to me prior to his confirmation,” said Mr Gardner, who is a Republican.

In pictures: 4/20 Marijuana world rallies Show all 26 1 /26 In pictures: 4/20 Marijuana world rallies In pictures: 4/20 Marijuana world rallies A man wears a marijuana leaf mask during the annual 4/20 cannabis culture celebration at Sunset Beach in Vancouver, British Columbia AP In pictures: 4/20 Marijuana world rallies A lady smokes marijuana on Parliament Hill on 4/20 in Ottawa, Ontario Getty Images In pictures: 4/20 Marijuana world rallies James Reed smokes a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies People sign a 4/20 sign on Parliament Hill on in Ottawa, Ontario Getty Images In pictures: 4/20 Marijuana world rallies A woman smokes marijuana on Parliament Hill on 4/20 in Ottawa, Ontario. Polling released showed strong support in Canada for a government drive to legalise recreational use of marijuana, but many would like the proposed minimum age for consumption to be raised. Sixty-three percent of respondents told the Angus Reid Institute they support legalisation Getty Images In pictures: 4/20 Marijuana world rallies A man smokes marijuana during the annual 4/20 marijuana rally on Parliament Hill in Ottawa, Ontario, Canada Reuters In pictures: 4/20 Marijuana world rallies Demonstrators smoke marijuana during the '4/20 Santiago' rally in favour of legalisation in front of the La Moneda presidential palace in Santiago, as part of the Global Marijuana March which is being held in hundreds of cities worldwide Getty Images In pictures: 4/20 Marijuana world rallies People play with a mock marijuana joint during a 4/20 party to demand legalisation and to celebrate marijuana culture outside the Senate building in Mexico City, Mexico Reuters In pictures: 4/20 Marijuana world rallies Adam Eidinger, co-founder of DCMJ, hands out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC Getty Images In pictures: 4/20 Marijuana world rallies In pictures: 4/20 Marijuana world rallies Police arrest Rachel Ramone Donlan after she handed out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC AFP/Getty Images In pictures: 4/20 Marijuana world rallies Police arrest Rachel Ramone Donlan after she handed out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC Getty Images In pictures: 4/20 Marijuana world rallies Thousands of people gather to smoke marijuana during the '420 Santiago'rally in front of the La Moneda presidential palace in Santiago Getty Images In pictures: 4/20 Marijuana world rallies People attend the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Kevin Barron and Lasean Moore of Raleigh, North Carolina, share a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Nic Ruhl takes a pull on a giant hand rolled joint at precisely 4:20pm MDT during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Various cannabis paraphernalia on display at a vendor's stall during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Mo Banez, of Austin, Texas, lights a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies A man displays a large container of cannabis during the Denver 420 Rally at Civic Center Park in Denver, Colorado. The rally, held annually, is a celebration of both the legalisation of cannabis and cannabis culture. Colorado is one of twenty-six U.S. states along with the District of Columbia that has legalised the use of cannabis either recreationally or medically AFP/Getty Images In pictures: 4/20 Marijuana world rallies Sitting in small groups on mats shaded by trees in the Rose Garden just across from the Knesset, participants lit up as the clock struck 4:20 for the local version of the traditional worldwide April 20 pro-marijuana events, known as '420' rallies Getty Images In pictures: 4/20 Marijuana world rallies An Israeli smokes a marijuana joint in Jerusalem during a rally at the Rose garden Getty Images In pictures: 4/20 Marijuana world rallies Sitting in small groups on mats shaded by trees in the Rose Garden just across from the Knesset, participants lit up as the clock struck 4:20 for the local version of the traditional worldwide April 20 pro-marijuana events, known as '420' rallies Getty Images In pictures: 4/20 Marijuana world rallies An Israeli girl poses with a mock marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current laws Getty Images In pictures: 4/20 Marijuana world rallies aelis pass around a marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current laws Getty Images In pictures: 4/20 Marijuana world rallies An Israeli smokes a marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current law Getty Images In pictures: 4/20 Marijuana world rallies An Israeli smokes a marijuana joint in Jerusalem on April 20, 2017 during a rally opposite the Knesset to celebrate 420 and express defiance of current laws AFP/Getty Images

In California, where a legal marijuana marketplace approved by voters in 2016 is only days old, members of both parties assailed Mr Sessions. Rep Dana Rorhbacher, an Orange County Republican, said the Attorney General had “delivered an extravagant holiday gift to the drug cartels”.

“By attacking the will of the American people, who overwhelmingly favor marijuana legalization, Jeff Sessions has shown a preference for allowing all commerce in marijuana to take place in the black market, which will inevitably bring the spike in violence he mistakenly attributers to marijuana itself,” Mr Rohrbacher said in a statement. “He is doing the bidding of an out-of-date law enforcement establishment that wants to see a perpetual weed war”.

Rep Ted Lieu, a Democrat representing the Los Angeles area, said Mr Sessions wanted to “take America back to the 1920s,” adding that “Prohibition didn't work then and it will not work now”.

California Bureau of Cannabis Control Chief Lori Ajax said she was conferring with the state's attorney general but had no plans to halt the state's rollout of recreational sales.

“We’ll continue to move forward with the state's regulatory processes covering both medicinal and adult-use cannabis consistent with the will of California’s voters, while defending our state's laws to the fullest extent,” Ms Ajax said in a statement.

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Colorado Republican Mike Coffman said in a statement that “Colorado had every right to legalize marijuana, and I will do everything I can to protect that right against the power of an overreaching federal government”. Alaska Sen Lisa Murkowski, also a Republican, called the announcement “disruptive to state regulatory regimes and regrettable”.

Oregon Senator Ron Wyden said Mr Trump had promised to let states establish their own policies but “Now he's breaking that promise so Jeff Sessions can pursue his extremist anti-marijuana crusade,” Mr Wyden, a Democrat, said on Twitter. Nevada Rep

State officials were defiant, saying they would not bow to federal pressure. Nevada Rep Dina Titus said she would “fight for businesses that are legally operating in states, contributing to tax bases, & creating jobs”.

“Make no mistake,” Washington Gov Jay Inslee said, “…we will vigorously defend our state’s laws against undue federal infringement”.

The mayor of Seattle, Washington's largest city, echoed her governor's statement in saying her police department would not alter its approach, saying in a statement that “Seattle won't be bullied by the Trump Administration”.