All the 33-year-old illegal immigrant wanted was a beer. After nearly a decade in this country, the Irish national knew to steer clear of police and federal agents. But he was stunned this month when a bartender at the Orpheum refused to serve him because his passport lacked a US Customs stamp.

The man grabbed his passport and fled, abandoning a $60 orchestra seat at a Ray Davies concert and igniting a debate over a new policy that one of the country's largest concessionaires imposed at the Orpheum and at another popular live-music venue in Boston.

Officials at the Boston Culinary Group said they started checking for customs stamps last year to ensure that passports are authentic, not to enforce immigration law.

But critics of the policy say that the stamp is no guarantee of validity and that checking for it is frightening to immigrants.

"I said, 'Who are you, immigration?" the man, a construction worker who spoke on a condition of anonymity because he fears deportation, said he asked the bartender. "It was a shock."

Daniel F. Pokaski - chairman of Boston's Licensing Board, which issues alcohol licenses - said he had never heard of local bartenders checking for a customs stamp before serving a customer.

"I wouldn't recommend it if, in fact, it does have the side effect of denying illegal immigrants the right to have a cocktail," he said. "I just think you're really taking a class of people, and based on the lack of a customs stamp you're denying them service. I'm not sure if I'm comfortable with that."

State law lists a foreign passport from a US-recognized country as an acceptable identification to verify that someone is 21, the legal age to drink. Other acceptable identification include a Massachusetts driver's license, a military card, a US passport, or a state liquor card, which shows someone is of legal age to drink.

The law does not mention a customs stamp, which shows the date of admission to the United States. But state and city officials say the company can legally increase its requirements, as long as it does not discriminate based on race, ethnicity, or other protected classes.

Boston Culinary Group launched the passport policy in September at Orpheum and the Bank of America Pavilion because bartenders were confused by the array of foreign passports, said company president Joseph Armstrong. Company officials decided that the customs stamp was a common denominator that could verify that the passports are authentic.

He said the company instituted the policy only at the two Boston halls because questions arose about passports and because alcohol is in high demand at concerts, making enforcement a major issue. The company serves venues across the country, from the Tsongas Arena in Lowell to Dolphins Stadium in Miami.