A New York state judge on Friday sided with green groups that sued the Department of Environmental Conservation for failing to promulgate regulations implementing a climate change law that the agency says would burden residents with high costs.

The 2019 Climate Leadership and Community Protection Act committed the Empire State to slashing greenhouse gas emissions in the coming years, but the DEC argued that implementing the act is "infeasible" because of the costs.

But New York Supreme Court Justice Julian D. Schreibman's Friday order said that's beyond the agency's authority to determine, and he gave the agency a hard deadline of Feb. 6 to come up with the required rules.

"While DEC notes that it has taken other, commendable regulatory steps to reduce greenhouse gas emissions, it candidly concedes that the impact of those regulations would fall far short of the 40% [and] 85% reductions mandated by the Climate Act, and therefore that such regulations do not 'ensure' compliance with the Climate Act," Justice Schreibman wrote.

Citizens Action of New York and other groups sued the DEC to force it to implement the law, which requires the state to achieve a 40% reduction in greenhouse gas emissions from 1990 levels by 2030 and an 85% reduction by 2050.

The justice said the DEC has met two of the three requirements the legislature gave it under the law, beginning with determining the statewide emissions limits necessary to achieve the requirements.

And he said the department met its obligation to convene a "climate action council" that would publish a plan with recommendations for attaining statewide emissions limits.

But the DEC hasn't completed the law's third step of issuing regulations to achieve the mandated emissions reductions.

Justice Schreibman rejected the DEC's argument that its situation is "complicated" and that it should be held to a less rigorous standard.

"It is undoubtedly true that the task placed before the DEC is very complicated indeed," he wrote. "But as a legal argument, this is unavailing. Respondent's proposition is without objective guardrails. A court is poorly equipped to determine when a circumstance is too administratively complicated for an agency to be ordered to follow the law."

He said the DEC argued that implementing the law is infeasible because it "would require imposing extraordinary and damaging costs upon New Yorkers" but ruled that the DEC doesn't have the authority to make that judgment under the act.

"The legislature has already decided that the Climate Act's goals 'shall' be achieved," the justice said. "The legislature has not empowered DEC to set its own targets, to achieve results within a range, or to simply to make progress. Instead, it has specified a result and required DEC to issue regulations that 'shall' fulfill it."

Bob Cohen, Citizen Action of New York's policy and research director, on Monday praised the court's decision.

"The decision confirms what we have stated over and over. The governor must comply with the crystal clear words of the climate law stating that the Department of Environmental Conservation must issue regulations ensuring that New York dramatically cut greenhouse gas emissions," Cohen said in a statement. "We hope the administration hears the message and acts rather than continue to stonewall by appealing."

The DEC on Monday said it's reviewing the decision.

The environmental groups are represented by Rachel Spector and Hillary Aidun of Earthjustice, Caroline Chen, Marinda van Dalen and Megan Carr of New York Lawyers for the Public Interest and Todd D. Ommen of Pace Environmental Litigation Clinic.

The state is represented by Meredith G. Lee-Clark, Krysten G. Kenny and Susan L. Taylor of the New York Office of the Attorney General.

The case is Citizens Action of New York et al. v. Department of Environmental Conservation, case number 903160-25, in the Supreme Court of the State of New York, County of Albany.