new york. In a major blow to landlords, a New York appellate court unanimously ruled Thursday that building owners who get tax benefits can’t deregulate apartments to raise rents. Developer Tishman Speyer was sued by rent-regulated tenants in Stuyvesant Town/Peter Cooper Village after the firm purchased the complex in 2006 and then tried to charge market-rate rents to pay off its $5.4 billion mortgage. The judges held the units must remain rent regulated until the buildings’ tax benefits expire in 2017.