How landlords gained the ability to remove apartments from regulation has a surprising backstory. Over the years, the Republican-dominated State Senate has often flexed its muscle to weaken rent stabilization at the behest of real-estate interests. Yet it was an overwhelmingly Democratic body that made the most important and far-reaching move. Shortly before Easter in 1994, by a 28-18 margin, the New York City Council implemented what is known as “vacancy decontrol,” which allowed a landlord to escape regulation and charge market rates once tenants moved out of apartments that cost at least $ 2,000 a month. Then-Mayor Rudolph Giuliani signed the measure into law.