Things could get very dark for beer lovers.

Surly Brewing Co. is suspending its 2020 installment of Darkness Day, a celebration of its yearly batch of Russian imperial stout. The two-day party and metal concert evolved out of earlier release days, when the black beer’s most committed fans would flock to the brewery to buy it.

The hiatus, which Surly announced in an e-newsletter Thursday, cites state laws that prevent the brewery from selling the beer directly to consumers in Minnesota. The law prohibits large breweries (those making more than 20,000 barrels a year) from selling 64-ounce growlers filled in their taprooms.

As the state’s third largest brewery — it produced 112,000 barrels in 2018 — Surly is a vocal opponent of the barrel threshold.

For the last two years, Surly was able to avoid the issue by holding Darkness Day in Wisconsin. Now, it wants to move the two-day festival back to Minnesota — but it won’t until state law changes.

“Every brewery that has a bottle release has it at the brewery, across the country. That’s kind of how you do it,” said Surly founder Omar Ansari. “We haven’t been able to do that because of the growler issues.”

Two state representatives introduced a bill Monday to raise the limit to 40,000 barrels. That wouldn’t help Surly, and the Minnesota Craft Brewers Guild is pushing a bill that would allow all Minnesota breweries to sell growlers, no matter the size.

“Knowing that was something they were going to bring forward, it seemed like a good time to put in our two cents,” Ansari said about the timing of the announcement.

Darkness Day began organically more than a decade ago, when fans of the beer congregated outside the brewery in the early morning cold so they could purchase the beer on the day of its release.

Over the years, the event grew larger, and Surly moved it in 2018 from its Minnesota production facility to an amphitheater in Somerset, Wis.

“We thought it would be great to have a beer festival, to add some components we didn’t have and control bottle sales a little more,” Ansari said. But the event drew fewer people than anticipated, and getting Surly staff and vendors to Wisconsin proved to be complicated.

“If we did it here at the brewery, where we have all the infrastructure — food, restrooms, parking — I think we could make an event that would be pretty spectacular,” Ansari said. “But we can’t do it for Darkness Day.”

Surly Darkness will continue to be brewed and sold in liquor stores.

The fall event takes several months to plan, but “we can react quickly if there was a change to the law this year,” Ansari said. He’s just not sure. “There are so many pieces to this, I don’t know.”

Ansari knows the loss of the festival, even if it’s temporary, will be hard on fans.

“This is something that’s been a big part of Surly,” he said. “It’s the fans that made it grow. It’s who we are.”