Maine’s beer industry is booming, and at the heart of the craft beer movement is a cadre of brewers who are pushing the limits of what beer can be, with sub-genres, niche products and a wide array of choices.

But lurking in state law is a 1937 provision that is confounding brewers and bar owners, who learned in recent weeks that displaying a beer’s alcohol content on signs or menus is illegal.

“(The law is) absolutely asinine,” said Greg Norton, whose store on Forest Avenue in Portland, the Bier Cellar, specializes in small-batch beer and wine. “It’s an important piece of knowledge for a customer, to plan how many beers they’re going to have that night.”

It’s unclear why the restriction was added to state law, which included rules for Maine’s post-Prohibition liquor industry with arcane terms such as “high test,” “high proof” and “pre-war strength.” Legislative documents from the time suggest it was aimed at advertisements that sold beer based solely on its strength.

Three-quarters of a century later, a state legislator is proposing to repeal the restriction and infuse what he considers to be a little common sense into the law.

The little-known rule resurfaced a few weeks ago in the Bangor area, when a state liquor inspector put the kibosh on a brewer’s listing of alcohol percentages, according to the Maine Brewers’ Guild.

Soon after that, inspectors were asking other brewers and bar owners to check whether they were out of compliance, said Dave Carlson, co-owner and brewer of the Three Tides restaurant and Marshall Wharf Brewing Co. in Belfast.

He said he learned of the regulatory initiative when he called his regular state liquor inspector Thursday to talk about a license renewal. The inspector had a different issue to discuss: He asked Carlson if he was listing alcohol percentages on his menu.

“I said, ‘Yeah, of course I was,’ ” Carlson recalled. “Then he asked me if I had a black marker” to black out the alcohol contents.

Carlson said the alcohol content is important information for a customer to have.

When he began serving craft beers about 10 years ago, he had to set a two-beer limit for some brews that were potent but easy to drink – in some ways a testament to a beer’s balance, he said.

Customers would come in dehydrated after a day of boating or golf, toss back a pint of a strong beer and have to take a breather.

“These guys were getting in trouble,” Carlson said. “We had to cut them off.”

Although Carlson hasn’t been cited or fined for posting alcohol percentages, the recent notices from state inspectors have sparked a wave of questions from bar owners.

It’s not clear why the regulators have raised the issue recently, or how aggressively they may enforce the law. Jen Smith, a spokeswoman for the Bureau of Alcoholic Beverages and Lottery Operations, did not return calls seeking comment about the policy Monday.

In response to the initiative, state Rep. Louis Luchini of Ellsworth has proposed an emergency bill to repeal the language about alcohol content and clarify the original intent of protecting consumers. He said that posting alcohol content ensures that consumers know what they’re buying.

“The craft beers can have a huge variance of alcohol content,” he said. “No one should be caught by surprise by a high-alcohol beer.”

Luchini said it could take months to change the law, as he seeks approval to submit the bill, lawmakers hold hearings on it and the Legislature moves it to up-or-down votes.

In the meantime, he hopes that regulators will find a way to work with brewers and bars so they don’t have to redact menus, only to rewrite them once the law changes.

Luchini said he plans to send a letter asking for guidance from the Bureau of Alcoholic Beverages and Lottery Operations.

Sean Sullivan, executive director of the Maine Brewers’ Guild, said the law’s original intent is now the exact opposite of the labeling that’s needed to make consumers safer. For his group, which is supporting the legislation, consumers’ safety is paramount, he said.

“This is just another example of the antiquated laws that just don’t make sense, given the current landscape of craft beer production,” Sullivan said.

Eric Michaud, who owns the beer-focused Novare Res bar at Canal Plaza in Portland and In’finiti, a brewery, distillery and restaurant on Commercial Street, said he learned about the law in 2009, when state regulators insisted that he change a poster advertising a beer festival, Bonjour! Fest.

Now in its sixth year and running this week at Novare Res, the festival features only beers with more than 9 percent alcohol.

“It wasn’t a way to advertise, ‘Come get drunk,’ ” Michaud said of the poster. “It was to say, ‘If you show up, it’s all strong.’ ”

Michaud said his understanding is that the law applies to advertising material displayed outside the bar. But he worries that the law, without a clarifying revision, is left open to wider interpretation.

“One day they’ll interpret it one way, another day it’s another interpretation,” he said.

Matt Byrne can be contacted at 791-6303 or at:

mbyrne@pressherald.com