The Transport Workers Union must pay $2.5 million for the strike that brought subway and bus service to a standstill for three days last December, a Brooklyn judge ruled yesterday.

State Supreme Court Judge Theodore Jones also penalized the union by halting its automatic collection of member dues. Union leaders had asked Judge Jones not to impose that penalty, which is expected to put a serious financial strain on the union during a time of waning union support among transit workers.

Union leaders had different predictions of how union members would respond to the financial crisis that yesterday’s court order could precipitate.

“Our members will stand firm,” the president of the Transport Workers Union Local 100, Roger Toussaint, said outside the courtroom yesterday.

Others predicted that bus and subway workers would be less likely to pay their union dues if those dues were not automatically deducted from their paychecks, as they were before Judge Jones’s ruling.

A member of the executive board of Local 100, Martin Goodman, pointed to the handful of union supporters present at the court yesterday as a signal that support for the union was low. Mr. Goodman suggested that the financial difficulty the union is expected to face is due not only to the court order, but also to the low morale among union members in recent months.

“I advise everyone to pay their dues on time. The only problem is there is so much dissatisfaction with the outcome of the fight,” Mr. Goodman said. Looking around the courtroom, he said: “I had rather there be an outpouring of sentiment. There are a dozen or two dozen workers, tops, here right now, out of a membership of 38,000. There has been no effort to mobilize.”

Other estimates put union membership at only slightly more than 30,000.

The cutoff of the automatic dues deduction is likely to force the union to downsize its operation and reduce personnel, a union lawyer told Judge Jones prior to the ruling. The lawyer, Terry Meginnis, said an order interfering with the union’s automatic collection of dues “will severely impact – in fact, cripple – the union in its ability to perform its function.”

Mr. Meginnis estimated the union collects $1.6 million in dues a month from its members, the vast majority via automatic deductions from paychecks.

Judge Jones suspended the automatic deductions indefinitely, but said that in three months the union may reapply to the court for that benefit. He ordered the union to pay the $2.5 million strike fine within a month, or to outline an acceptable payment plan.

At the time of the strike, which lasted from December 20 to December 22, Judge Jones had told the union he would impose a $1 million penalty for each day the strike lasted.

Lawyers for the MTA depicted the union as a financially solvent organization that sought to give the impression of operating under financial strain through bookkeeping maneuvers. An attorney for the transit authority, Neil Abramson, said the union has underreported the value of its union headquarters and has not recently attempted to collect its dues through a voluntary collection system.

Mr. Goodman said he reacted to Judge Jones’s ruling with “anger, extreme anger.” He also said he never predicted Judge Jones to issue a ruling favorable to the union. Mr. Goodman said Judge Jones’s decision last week to send Mr. Toussaint to jail gave him a sense of “dark foreboding.”

Judge Jones assigned no blame for the failure of the two sides to reach a new contract for transportation workers in the days leading up to the strike. Under the Taylor Law, it is illegal for public employees to strike in New York.

“I have no opinion on the negotiation tactics of either side,” the judge said.

Judge Jones followed his order yesterday with a terse statement similar to what he said in the past: “This is an unfortunate event and an unfortunate day in the history of labor relations in this city.”

Mr. Toussaint, whose jail sentence is not scheduled to begin before the end of the month, emerged from the courtroom flanked by civil rights activist Jesse Jackson.

Mr. Jackson said transit workers in New York have been “pushed against the wall. Workers in New York stood up for the best in the labor movement in America.”

The union will appeal yesterday’s rulings, Mr. Toussaint said. “Unfortunately, the courts are being used for political purposes to intimidate the labor movement,” he said.

Judge Jones’s handling of the transit strike is already under review by an appellate court. Just hours before the decision yesterday, a mid-level appellate court heard arguments about whether the judge had the authority to fine the union. A union attorney, Arthur Schwartz, argued that a jury should have heard the case and decided the issue of a fine. The city’s corporation counsel, Michael Cardozo, argued that the fine Judge Jones handed down should be upheld on the grounds that quick action, and not the empanelling of a jury, is required when public employees strike.

“The clear purpose of the law is not to penalize the union, but to do whatever can be done to prevent an illegal strike,” Mr. Cardozo said.