D.C. 33 President Pete Matthews said that his union was still willing to bargain and that Nutter's desire to implement terms unilaterally is typical of the way he negotiates.
"That does not surprise me. I've said it in the past: He tries to act like a dictator. He dictates terms," Matthews said.
His union has been working on frozen wages without a contract since 2009. Both sides say they are frustrated with the standoff, and Nutter's move on Friday was the most serious effort yet to end it.
But it looks like an uphill battle for the administration. In 1993, a Commonwealth Court ruled that the Philadelphia Housing Authority was not allowed to impose terms on some of its workers so long as they didn't strike.
Shannon Farmer, the city's chief negotiator, said Friday that the facts of this case - D.C. 33 has been without a contract for years, for instance - will lead to a favorable decision.
Nutter says an overhaul of pensions and work rules for city workers is necessary for the city's financial health.
Union leaders contend that the city can pay for its workers since it balances its budget every year and can still afford projects like the Dilworth Plaza renovation outside City Hall, which will cost tens of millions of dollars.
Besides city money, the plaza's renovation is being bankrolled by federal transit money, SEPTA, the Center City District and other funding sources.
On Twitter: @SeanWalshDN