Elected officials, police officers, and bartenders at Irish pubs are among those who are livid over a St. Patrick’s Day liquor ban on New York’s commuter railroads, calling the move a gross act of stereotyping and discrimination.

Anticipating an inebriated crowd commuting into and out of Manhattan to celebrate the holiday along the parade route Saturday, the Metropolitan Transportation Authority’s two commuter railroads, the Long Island Rail Road and Metro-North Railroad, are banning alcohol from their property that day and into early Sunday, making the Roman Catholic feast day the sole religious holiday when bar cars are closed for business and stations and trains run dry.

“It definitely looks like stereotyping, and that’s what the MTA should be faulted for,” state Senator Martin Golden, a Republican of Brooklyn who is Irish, said. “Some people do get out of control, but to focus on that day, and on certain segments of the population like that, is totally wrongheaded.”

Mr. Golden said the MTA should lift what he dubbed a discriminatory liquor ban that assumes Irish revelers are more out of control than other groups when celebrating their holidays.

“We want to maintain orderly travel,” a spokeswoman for the Long Island Rail Road, Susan McGowan, said. “It’s a day when we have more ridership than usual, and when there can be disruptions related to alcohol.” Both commuter rail lines also ban alcohol from their property on New Year’s Eve, and the Long Island Rail Road also prohibits alcohol on trains and in stations in anticipation of the annual Belmont Stakes horse race.

“It’s not fair that on other holidays they don’t ban alcohol if they do it on St. Patrick’s Day,” Don Rogers, a vice president of a large New York Police Department Irish fraternal organization, the Emerald Society, said. Mr. Rogers also noted that the New York Police Department steps up enforcement of rules prohibiting drinking outside during the St. Patrick’s Day parade — rules it is more likely to overlook for other parades, such as the Hispanic Day and Gay Pride parades. “Those laws should be enforced all the time, not just in this parade,” Mr. Rogers said.

A police spokesman, Deputy Commissioner Paul Browne, said the police department does not comment on MTA policy.

Bartenders in predominately Irish neighborhoods expressed dismay over the liquor ban. “People drink on all holidays, so why do the railroads single out this day in particular?” a bartender at Woodside’s Irish Pub Cuckoo’s Nest, Sandy Gauneau, said.

As leaders like Mr. Golden say they want the MTA to lift the ban, more conciliatory Irish political figures, like the speaker of the City Council, Christine Quinn, are lending their support to the liquor ban on the grounds that there is no dearth of drinking establishments in Manhattan open on St. Patrick’s Day.

“LIRR has made a sensible decision,” Ms. Quinn said. “One that will serve to minimize disruptions from commuters who may have already had one too many.” Ms. Quinn herself will not be participating in the parade festivities this year. She plans to be in Dublin.

Metro-North railroad typically runs 16 bar cars out of Grand Central Terminal, and on weekdays sells alcohol on bar cars along the New Haven line. The Long Island Rail Road also sells alcohol at many of its station platforms and aboard its Hamptons-bound trains during the summer season. Both railroads allow passengers to bring their own alcohol aboard. This weekend, however, customers caught with open or closed containers of alcohol will be fined about $50.

An MTA task force is reviewing the alcohol-friendly policies on board its commuter trains, following the death of an inebriated teenager, Natalie Smead, last summer at the Woodside station. The task force will bring its findings before the board in the next few months.

Even some diehard St. Patrick’s Day revelers said they see some logic to the MTA’s alcohol ban. “I’m not offended by it,” a bartender at Ryan’s Pub in the East Village, Steven Goldrick, said. “The train should be a good opportunity to take a rest from all of the drinking.”