On a recent Saturday evening, John Nielsen stands behind the long glass display showcase lined with fluorescent-lit, glass-blown pipes at the North Boulder head shop Rocketman, listening to Led Zeppelin.

A Jimmy Page solo hits a high-pitched, staccato climax and John springs from behind the counter as a woman enters the store and deposits a shaggy black lapdog named Oreo onto the carpet to play with Oggy and Noni, the white Shih Tzus that are fixtures of the store.

The woman has been using kratom, the leaves from a tropical tree native to Southeast Asia, to treat shoulder pain. She lifts her left elbow up head high, reporting to John that it works. Given its success, she’s convinced her mother to try it after an upcoming surgery in place of pharmaceutical painkillers.

“She likes the pain pills, the feeling. But I told her that (kratom) works really well,” she says.

Kratom is often sold in the form of a dry leaf powder in the U.S., where it is consumed in capsules, mixed into drinks or brewed into tea. Over the past decade, the botanical has gained a reputation as a natural alternative to prescription painkillers and a legal treatment for opiate withdrawal, despite claims from federal drug regulators who claim it poses a risk to public health.

Within cultures where the plant grows, it has been used for centuries as a traditional medicine, but it remains relatively overlooked by Western science.

In September, kratom was thrust into the public spotlight when the U.S. Drug Enforcement Agency (DEA) said it would put a two-year ban on the plant as early as Oct. 1 by placing its active substances on the Schedule I list of narcotics, which includes heroin and GHB (sometimes called the “date rape drug”), among others.

The DEA also declined to take official feedback from the public, under emergency authority to ban kratom as “an imminent threat to public safety.”

With no official means of rebuttal, the ban appeared imminent, leading kratom supporters to make public video testimonials detailing the plant’s medical application in their life. Two weeks after the notice, 120,000 people had signed an online petition urging the president to stop the ban.

The outcry of support received widespread media coverage, and ultimately evoked two congressional groups, consisting of 51 U.S. Representatives and 10 members of the Senate. These groups of elected officials rebuked DEA Administrator Charles Rosenberg for using unilateral action against a botanical, urging him to allow public comment.

Facing a 30-day countdown from regulators, the American Kratom Association, a two-year-old interest group of consumers and vendors, had about $30,000 in its bank account.

“I thought for certain that I’d be able to raise a substantial amount of money in a very short amount of time, which I was able to do,” says the Denver-based group’s founder Susan Ash.

The money was quickly used to hire lobbyists, political consultants and, particularly, lawyers. Ash, who had researched other emergency Schedule I fights, anticipated a legal battle. The group’s lawyers, which Ash said were former FDA attorneys, told her there was a 10 to 15 percent chance of achieving the unprecedented reversal from regulators.

Responding to federal group action, the Denver Department of Environmental Health seized all kratom-containing products from Denver-area retailers. For one, Rocky Mountain Kratom, that meant closing the doors entirely and delaying the opening of its new south Broadway store.

On Oct. 13, the DEA rescinded its emergency order, announcing the opening of a six-week public comment period ending Dec. 1. After the period ends, federal regulators will examine the comments, along with an analysis from the Food and Drug Administration (FDA). The American Kratom Association has also commissioned its own analysis to challenge that of the FDA. It is being prepared by Doctors Jack Henningfield and Reginald Fant of Pinney Associates.

While the comments period allows some reprieve from an illicit drug schedule, it does little to rid many kratom users and business owners of the anxious feeling in their gut brought on by uncertainty.

For kratom users like Ash, who uses the plant to treat chronic pain and previously used it to treat withdrawal and help her get off painkillers, a ban might mean she’d have to return to an opiate to treat her pain.

“If they do decide to ban it, I have to make a decision of whether or not I want to go back onto something like Suboxone,” she says.

Suboxone, the brand name of buprenorphine, is a semi-synthetic derivative of the opioid thebaine. Like other opiates, Suboxone binds to opioid receptors, providing less stimulation than its more potent relatives.

The drug is all-too familiar to Ash, who previously abused the drug, taking more than her therapeutic dose to get more effect.

Ash began taking opiate painkillers in her mid-30s as doctors attempted to alleviate the pain caused by advancing Lyme disease that they had mistakenly identified as Fibromyalgia.

Ash says the pills prescribed worked, too. For years, she took morphine to take the edge off of pain that had previously left her bed-ridden. Eventually, her body adapted to the drugs, and the pills stopped working. To alleviate Ash’s crippling pain, doctors upped the morphine dose, bringing some of the punch back to her pills, for a time.

As the doses climbed, Ash says she stuck to her doctor’s prescription, rather than doubling up doses or seeking more pills from an illicit source. When her sister and brother-in-law expressed concern about her drug use, she was surprised, but agreed to see an addiction doctor with the couple.

The doctor prescribed Suboxone, but failed to give her proper instructions on how to use the medication. Due to buprenorphine’s ability to create a strong bond with receptors, it essentially bumped the morphine from the receptors and attached itself, to deliver a much weaker stimulation.

“You’re supposed to take Suboxone when the withdrawals start and not before,” Ash says. “If you take it before, you go into something called precipitated withdrawals, which are 100-times worse.”

The idea is to use Suboxone to mollify vacant receptors preventing or lessening the withdrawal.

For Ash, the precipitated withdrawals started with a runny nose and evolved into severe flu. The experience left her in agonizing pain, with diarrhea and unable to sleep or eat for the next 10 days.

It was her first experience with withdrawal, but it wouldn’t be her last. She later relapsed because of the depression that gripped her life after the physical pain passed, she says.

Unlike before, though, she began taking the pills more frequently, and was left with no pills between prescriptions, often meaning withdrawals. During one of the withdrawals, she got online and pleaded with fellow members of her Lyme disease support group on Facebook.

“I claimed my pills were stolen, which they weren’t, I just ran out early,” she says. “I was like, ‘I’m so desperate, I’m in so much pain and sick from withdrawals, can anybody out there help me?’ I fully expected somebody in the support group was going to say, ‘OK, I’ve got extra narcotics, so I’ll just send you mine and break the law.’”

A woman in the group sent Ash a message, saying there was a plant that could help. She asked Ash to call her, so she could explain it.

“I thought she was crazy,” Ash says. “There’s no way a plant is going to be able to help me.”

Each month, her pill prescription began running out earlier and earlier, and amidst withdrawals, she decided to call the woman.

“I had an order Fedexed to me, and I started kratom the next day,” she says. “It basically made my withdrawals — not go away — but it made them manageable.”

For several years, Ash relied on kratom to protect against withdrawal when she needed it.

During her last rehab stay, doctors told her she’d likely need to take Suboxone for the rest of her life to treat chronic pain.

“It (Suboxone) was acceptable to me at first, but I realized I was getting into patterns of abuse with it too, saving my doses up in the day to feel more powerful at night,” she says. “I began to wonder if kratom might actually help me get off of Suboxone, which it did. I used it to taper off Suboxone.”

Nearly three years ago, she began using kratom exclusively for chronic pain treatment.

“I’ve never gone back,” she says. “I’ve never had a craving for a narcotic, and I no longer consider myself a chronic pain patient while I’m taking kratom.”

In 2014, Ash founded the American Kratom Association, a pro-kratom interest group funded by donations from consumers and vendors.

The group has benefitted from a large surge in kratom usage, which the Association estimates is between 3 and 5 million people, based on the tonnage of kratom imports and number of customers of its largest vendors.

The demand for viable addiction treatment options in the U.S., where 90 percent of the world’s opiates are consumed, has never been higher. In 2014, overdose deaths from opioid drugs was higher than any other year on record, accounting for more than six of every 10 overdose deaths in the country, according to a Department of Health and Human Services report.