The suit, filed Tuesday in state Supreme Court in Manhattan, seeks to resolve a question of separation of powers at a time when the council has become increasingly restive.

The legal wrangling underscores an unfortunate reality for the council and its outspoken speaker, Corey Johnson: New York City’s charter gives broad and strong authority to the mayor in most areas, so much so that members are left fighting over the ability to simply file paperwork in court that usually has little effect on the ultimate outcome of cases.

The fight over powers stems from a court defeat earlier this year: Five council members attempted to file a brief in support of homeowners, renters and others who had sued the city over its property tax system. A state Supreme Court judge ruled they could not do so under the City Charter.

But while that case is on appeal, some council members have been eager to file briefs in support of plaintiffs in other cases against the city, notably in support of the tenants of public housing who have sued the New York City Housing Authority over conditions in their apartments. At least three members sought to file an amicus brief, but were effectively denied by the Law Department.

“NYCHA’s unlawful failure to keep residents safe from toxic substances and ensure their continued access to heat and hot water constitute a public health emergency — and indeed a humanitarian crisis,” the three council members, Laurie Cumbo and Alicka Ampry-Samuel of Brooklyn and Ritchie Torres of the Bronx, wrote in their brief. “The court’s immediate intervention is necessary.”

The courts did intervene Tuesday on behalf of NYCHA tenants, as a judge in the public housing tenants’ case ruled against the housing authority and ordered it to test thousands of apartments housing children for lead paint.

But given the Law Department’s opposition to council members filing briefs in support of plaintiffs in these sorts of cases, the council’s own lawyers decided to ask a court to settle the question — not merely in the context of this case, but for all cases.

“We’re not supposed to always agree and that’s fine. But we must always be allowed to speak, including in court cases that affect our districts,” Johnson said in a statement.

The argument is ultimately over whether the council is an agency under the charter, or a separate and coequal branch.

The city’s Law Department does represent the council in many matters and has argued that the charter makes the corporation counsel — who heads the Law Department — the sole attorney for the city and every agency, which the Law Department believes includes the council. If the corporation counsel declines to represent them, this theory holds, members could file briefs as citizens, but not in their official roles.

But the council’s lawyers argue that council members should be allowed to hire outside counsel and express their own opinions on a given matter — on the grounds of a separation of powers and because of the members’ First Amendment right to speak on behalf of their constituents.

In March, the three council members asked the corporation counsel, Zachary W. Carter, to represent them for the purpose of filing the brief or authorize them to hire outside counsel. Carter “denied the request by not responding to it,” according to the council’s suit, and in doing so “committed an error of law and acted improperly, arbitrarily, capriciously, and unreasonably.”

The council is represented in the case by the firm Emery Celli Brinckerhoff and Abady.

“The responsibility for representing the official position of the city in court is vested in the Corporation Counsel,” a Law Department spokesman said in a statement. “This fundamental principle — that a government must speak with one official voice in litigation — is true at every level of government — local, state and federal.”

This article originally appeared in The New York Times.

J. DAVID GOODMAN © 2018 The New York Times