There’s been a shift in the ground rules governing BYOB or “Bring Your Own Bottle,” a cornerstone of the foodie and cheap-eats scene in Chicago. What’s more, the change has flown under the radar, due to bureaucratic miscommunication over several years. The policy affects nearly 4,800 licensed restaurants in the city.

The rule in question governs so-called “corkage fees,” which restaurants place on diners who bring their own unopened wine, beer and other liquor. Until last week, the city’s Department of Business Affairs and Consumer Protection warned present and prospective restaurant owners that — unless their restaurants had liquor licenses — they could not impose such fees.

Several documents, including the City of Chicago’s Restaurant Guide had read “no direct or indirect fee may be charged for the allowance of alcohol consumption without a City of Chicago liquor license; this includes corkage fees.”

The policy’s effect allowed, say, a fine restaurant that sold its own wine to charge a customer $75 if she brought in her own. Restaurants that choose to forego a liquor license (or couldn’t afford one) could allow customers to bring their own liquor, but charge no fee.

Now, BACP wrote in an email that this rule had been stricken by the department’s commissioner sometime around 2007 or 2008. Requests for documentation or further comments were declined. The error in documentation came to the department’s attention when WBEZ’s Curious City mentioned the rule in its investigation of why Chicago has so many BYOB restaurants.

“A section of the city’s website inadvertently had outdated information regarding corkage fees. The information has been removed,” wrote Mika Stambaugh, BACP’s Director of Public Information. (Archived copy of the former Restaurant Guide.)

The change in policy toward corkage fees hasn’t been addressed directly by Chicago’s City Council, despite the fact that aldermen have repeatedly debated BYOB policies and often sided with consumer-friendly policies.

For example, in 2014 aldermen voted to give themselves the authority to put BYOB off-limits at pool halls and other businesses that sometimes allowed the practice. Aldermen explicitly exempted BYOB at restaurants in those rules.

Concerning the corkage fee rules changes, Alderman Scott Waguespack (32nd) said “It would help to have open, public hearings on this in the licensing committee of the City Council so that businesses or people affected by the Bring Your Own Bottle policy would know exactly what it is and allow people to speak for or against it. And then make sure the city has the right policies on paper that both the city and the aldermen are giving out to anybody concerned about this issue.”

Corkage fee rules are currently governed by BACP and Liquor Control commissioners, not City Council, according to Daniel Rubinow, a former prosecutor for BACP.

“When you’re charging corkage fees, you’re getting very close to the service of alcohol, which is highly regulated,” said Rubinow. That could be what led to the language in question — an effort to keep businesses without liquor licenses from “serving” alcohol.

The miscommunication may have influenced hundreds or thousands of BYOB restaurants in Chicago to not charge corkage fees. A BACP representative was quickly quoted in 2013 as saying the department “ cleaned that up years ago,” but the erroneous documentation and instructions to business owners continued for three more years.

In 2009 Mixteco Grill in the Ravenswood neighborhood was visited by a Chicago police officer who said they’d received complaints about charging a corkage fee.

“They told us that we couldn’t charge and gave us a warning,” said Ismael Garay, a manager at Mixteco. “They told us that we couldn’t do that.”

Mixteco immediately changed their policy.

When asked if they would re-institute the corkage fee given the City’s new stance, Garay said they probably wouldn’t.

“We do pretty well without it. It would be kind of hard, maybe like a week ago Rahm Emanuel was eating here,” said Garay. “How are we going to charge him a corkage fee?”

That may be the most prudent decision, says Rubinow, the former prosecutor who now specializes in liquor license law.

“It does not surprise me that there’s been a reinterpretation or at least clarification about what the rules mean,” said Rubinow. “However, I think that you always expose yourself when you’re in this kind of grey area.”

So BYOB diners should be prepared to be charged a fee for opening their wine, beer or liquor bottles. And restaurant owners are free to charge them, though Rubinow would advise restaurant owners to proceed with caution.

“All it takes is a change from a local liquor control commissioner deciding how they’re going to change these rules or maybe even pressure from the aldermen for them to say, ‘Look, this is out of control. How can we stop this?’”

How will regular diners take this change? Ian Adams asked the Curious City question that started this whole thing. He says it won’t lessen his appreciation of BYOBs.

“I’m more intrigued by the murky regulation that seems to underscore the confusing and sometimes totally unclear regulations and rules that go around this. I’m glad I’m not a restaurant owner trying to navigate these rules.”