The Massachusetts Alcoholic Beverages Control Commission issued an advisory yesterday that has some brewers scratching their heads -- and probably worrying about their futures.

The ruling apparently will make it more difficult for small beer makers to get licensed. Many of the state's breweries have what are known as farmer-brewery licenses, which are less expensive and less cumbersome to obtain than full manufacturer license. The licenses also allow breweries to distribute their own beer locally, sell beer on premises, and operate tasting rooms.

The ABCC's advisory -- which followed its decision last week to deny an application for a farmer-brewery license from a new beer maker called Idle Hands Craft Ales -- says a business can get a farmer-brewery license only if at least 50 percent of its beer-making ingredients are grown in Massachusetts. That would pretty much disqualify every brewery in the state.

None of the roughly two dozen breweries that currently have farmer-brewery licenses will be grandfathered, either. "The Commission put the industry on notice that it will apply this ruling prospectively and, specifically, during the next annual renewal cycle to ensure that every applicant for a Farmer-Brewer license meets the state law definition of farmer-brewer," the advisory says. "Moreover, applicants that do not meet the criteria for a Farmer-Brewer license are welcome to apply for a manufacturerâs license." (Some breweries hold both licenses.)

The law creating the farmer-brewery license was written "for the purpose of encouraging the development of domestic farms."

Representatives of Sam Adams and Harpoon declined to tell us whether they think the advisory would affect their popular tasting rooms.

More to come on this developing story. The full text of the ABCC's advisory is below.