Black Hammer Brewing in SoMa debuted a very special beer for the 4/20 holiday in 2017: Toke Back Mountain, an IPA brewed with cannabidiol, the hemp-derived compound better known as CBD. The brewery said it was California’s first cannabis beer.

Since then, Black Hammer has done brisk business in the cannabis beer category, releasing eight brews containing CBD. “They’ve been extremely well received,” says owner Jim Furman. “Our line of CBD beers has been our most popular line.”

But a few weeks ago, the federal Alcohol and Tobacco Tax and Trade Bureau ordered Black Hammer to cease production of all its CBD beers.

Why? It’s not because of any federal laws around cannabis. Rather, it’s because the bureau requires special approval for any non-standard beer ingredients. Plenty of materials that are food-safe aren’t on that list, so breweries will often apply for special approval of their formula when they want to use one.

What qualifies as standard versus nonstandard might surprise you, in fact. Rose hips are fine; rosewater is not. Guava is OK, but not passion fruit.

Hemp is not on the list. Nor are terpenes, the compounds that Black Hammer uses to imbue beers with that dank cannabis flavor. (The hemp-derived CBD does not have any flavor on its own.)

CBD is a non-psychoactive cannabinoid. That means it won’t get you high, unlike the most famous cannabinoid, THC. Many users tout CBD’s effectiveness in pain reduction, anxiety relief and even alleviation of seizures.

When Furman first released the CBD beers more than a year ago, Black Hammer was “approaching it more from a CBD legality standpoint than a formula approval standpoint,” he says.

The brewery will, of course, comply with bureau regulations, and has already begun the process of applying for approval for hemp, so that it can resume CBD brewing.

In the meantime, Black Hammer can continue to sell the CBD beers it has already produced. So on Thursday, the company will put its last remaining keg of Toke Back to the Future, an American pale ale with 5 milligrams of CBD per serving, on tap beginning at 4:20 p.m. After that, every Tuesday will mark the release of a different CBD beer, and bartenders will run the kegs throughout the week until they’re kicked. That system should last nine weeks, and Furman will announce via Instagram which beer will be each week’s special. For now, the CBD beers will be available only to drink at the SoMa taproom; off-site consumption is verboten.

One concern lingering for Furman: the recent failures of Congress to reclassify hemp under federal law, so that it would be considered an agricultural commodity rather than a controlled substance. That could make hemp’s formula approval a little bit different from, say, rosewater: “We believe that future approval of our formula may be dependent on hemp reclassification by the federal government/DEA,” he wrote in an email.

Still, Furman remains hopeful that he’ll brew CBD beers again, ideally by the time Black Hammer’s new brewpub, called Wilkommen (“welcome” in German), opens. Although a location has been secured — Market Street at Sanchez Street — Furman won’t yet share information about an opening date.

“Our guests love the CBD beers, and we’re pretty sad that we have to stop producing them,” he says. Of the eight CBD beers he has created, Furman considers Hippie Hill, an imperial IPA, to be his greatest success. Brewed with Tahoe OG terpenes, “it’s unmistakable. So fresh,” he says. “It’s got the most dialed-in cannabis flavor profile.”

Black Hammer Brewing, 544 Bryant St., S.F. 415-500-2273 www.blackhammerbrewing.com

Esther Mobley is The San Francisco Chronicle’s wine, beer and spirits writer. Email: emobley@sfchronicle.com Twitter: @Esther_mobley Instagram: @esthermob