Just after 11 a.m. yesterday, the lawyer for the City Council’s Committee on Education carried a manila envelope down the steps of City Hall and around the block before marching through the front doors of Tweed Courthouse.

By 11:15, the transaction was complete: The counsel, Mark Goldey, had served the city’s Department of Education with a subpoena, requiring the attendance of the chancellor’s senior counselor for school intervention and development, Rose Albanese DePinto, at a hearing Tuesday on a new city law forbidding bullying at schools.

When Ms. DePinto failed to show up Monday morning at a council hearing on the Dignity for All Students Act, the education committee chairwoman, Eva Moskowitz, threatened to call a vote to issue a subpoena if no one contacted her within 48 hours.

The only word Ms. Moskowitz received in the two days that followed was a harshly worded letter from the department’s top lawyer, Michael Best.

“Because we are not implementing the law as a result of its illegality, there is no purpose to be served by our testifying with respect to our implementation efforts,” Mr. Best wrote. “If we were to testify, we would once again repeat what we have said here, i.e., that the law is illegal and is therefore not being implemented.”

Mr. Best also reminded the council that it was free to sue if it disagrees with his legal interpretation.

Ms. Moskowitz and her colleagues were not deterred by Mr. Best’s memo.

“The mayor could decide at this point he’s not going to answer the council’s questions about the budget, the mayor could decide that he’s not going to answer questions about the way the police function,” Ms. Moskowitz said before her committee voted unanimously to issue the subpoena. “This is not even about specifically the Department of Education. It is about the legislative authority of this body.”

The Upper East Side Democrat said she never imagined when she was a civics teacher that she would have to give the mayor of New York City a lesson on the importance of the separation of powers.

Other members expressed similar anger.

A Brooklyn member, Bill de Blasio, said it was the city’s responsibility to bring legal proceedings if it doesn’t think the anti-bullying act is legal – not the other way around.

A Manhattan Democrat, Robert Jackson, put it more bluntly.

“I’m ready to rumble with the mayor and his people,” he said. “The City Council will not stand for the executive branch telling us what we can do and what we can’t do. … You’d better believe that we’re going to do everything in our power to ensure that the mayor carries out the laws of the city of New York … and I say Mayor Bloomberg, you’re wrong. Get with the program and get with the law.”

After the vote, Mr. Goldey fetched a signature from Council Speaker Gifford Miller before delivering the official document to Tweed.

It was the first time the council used its subpoena power since 2001, when its Parks, Recreation, and Cultural Affairs Committee pressured the parks commissioner, Henry Stern, to hand over documents about how he was spending money.

Mr. Goldey said if Ms. DePinto doesn’t show up for next week’s hearing, she could be held in contempt of council and jailed.

In a statement issued early yesterday afternoon, Mr. Best said education officials were resolute in their decision not to come before the council for a third time to speak about the law on bullying.

“Rather than go to court and seek a ruling on the validity of this law, the council appears interested only in political grandstanding,” he said.

By day’s end, though, Mr. Best said Ms. DePinto would testify Tuesday, to avoid prolonging the dispute.