The $17.7 billion acquisition of Cablevision by France-based telecom giant Altice marked the end of an era for the New York media world in 2016. The longtime cable operator was rebranded, though its Optimum system kept its name, while and Cablevision’s omnipresent Dolan family refocused its attention on Madison Square Garden and other pursuits.

But the Dolans are not ready to go gentle into that good night, apparently. In a lawsuit filed today in Delaware Chancery Court, the family says Altice violated the merger agreement and also committed fraud, principally for allegedly starving the hyper-local News 12 Networks of resources. Altice also has laid off dozens of workers, the suit says, and plans to get rid of established 60-year-old anchor Colleen McVey because executives allegedly sought a “fresh look” for its on-air talent.

Along with McVey, the plaintiffs are Charles Dolan, founder and former CEO of Cablevision; Helen Dolan; James Dolan,...