The US Drug Enforcement Agency took an unprecedented step this week that the agency says signals a substantial shift in its direction, after decades as a leader in the US war on drugs.

After the DEA imposed its strictest drug regulations on a south-east Asian plant called kratom, the outcry was strong and immediate. Many have cited the plant as an effective treatment for addiction to prescription painkillers and other opioids, while evidence of the drug’s harms, they said, is minimal.

In response, the DEA handed a major victory to drug reform advocates: it reversed its decision and halted the emergency scheduling of kratom.

“This is an unprecedented action. It’s never happened before,” said agency spokesman Russ Bayer. “We’ve never withdrawn a notice to temporarily schedule any substance but we want to move through this process in a transparent manner.”

“I am thrilled and also surprised,” said Marion Winik, a Baltimore-based writer and professor who has used kratom for several years. “I was so sure that big pharma, not to mention the alcohol lobby, had the door nailed shut.”

Bayer says that the decision is an indication of a changing approach at the agency under acting director Chuck Rosenberg, who was appointed to the position a year ago after his predecessor, Michele Leonhart, resigned in the wake of a mishandled sex scandal in the agency.

“We have had kind of a cultural, organizational transformation during the past year,” Bayer said. “Our core mission has remained the same. It will always be to go after the biggest, most sophisticated, most violent drug traffickers and organizations responsible for the supply of drugs. But Mr Rosenberg has brought in an added emphasis, an increased awareness of some of the other functions that DEA needs to be engaged with. First and foremost community outreach, educating the public in terms of drug abuse, talking about addiction as being a disease.”

Grant Smith, deputy director of national affairs at the Drug Policy Alliance, called the announcement “a truly remarkable moment” for an agency “with a long track record of ignoring both science and public opinion”.

The DEA has for decades been at the forefront of the US war-on-drugs approach. Even Rosenberg, as many states moved to legalize marijuana, called medical marijuana a “joke” last November. The comment drew more than 100,000 signatures calling for his resignation.

The agency announced in August that it would place kratom in the most restrictive classification of drugs, Schedule I, along with heroin, marijuana and LSD, at the beginning of October. “Since publishing that notice, DEA has received numerous comments from members of the public challenging the scheduling action,” the agency posted in a note to the Federal Register on Thursday.

Bayer said the agency will solicit final comment through 1 December. “We want to take into full consideration the public comment together with the FDA’s medical and scientific evaluation,” he said.

Many users claim that kratom, which is botanically related to the coffee plant but also works in the brain’s opioid receptors, can be used to treat opioid addiction, which has become a major political issue as overdose deaths have soared and touched the lives of many white middle-class families. Lawmakers including the Republican senator Orrin Hatch and Democratic senator Corey Booker wrote to the DEA opposing the proposed emergency scheduling.

Susan Ash, the head of the American Kratom Association, says she became addicted to opioid pain medicine and struggled until she found the plant – which is now entirely unregulated and sold at paraphernalia shops, health food stores and online. “Literally within a two-week period of time, I was up and around and productive,” she said.

“I can’t express my relief that I’m not going to be turned into a felon over this,” Ash said. “But it is a relief that comes with a lot of caution. And knowing that we have an even tougher job ahead of us to prove to the DEA and the FDA that this is not the harmful dangerous substance that they’re claiming it to be.”

Bayer says another indication of the agency’s shift in approach is its decision to allow more universities to grow marijuana for research purposes. Before the August announcement, the DEA required the National Institute on Drug Abuse to contract with only one university, the University of Mississippi. But at the same time as that announcement, the DEA denied a petition to reschedule the drug and officially designate it as having medical value, which would have had a dramatically more substantial impact.

While advocates of drug policy reform are encouraged by the decision, many remain skeptical.

“We’re going to need to see more from them,” says Smith of the Drug Policy Alliance, which is calling for an overhaul of the scheduling system as a whole. “Since the DEA was founded in the 1970s, its track record has been to ignore science and ignore public opinion on how it makes decisions on drug scheduling.”