The royal rumble involving Princess Grace of Monaco’s grandson at a Manhattan club is turning into a free-for-all in court. After Pierre Casiraghi and two of his pals filed suit against businessman Adam Hock and the Double Seven nightspot over the battering they took in February, Hock and the club are swinging back at Casiraghi’s crew — and each other. In reply papers filed in Manhattan Supreme Court, Hock claims that Casiraghi, art dealer Vladimir Restoin Roitfeld and banker Diego Marroquin were the aggressors in the violence in a VIP area in the early hours of Feb. 18, reports The Post’s Dareh Gregorian. Hock claims the trio was obnoxiously helping themselves to his vodka, and were “visibly intoxicated” before attacking him in an “unprovoked and unjustified assault.” Hock also faults the club and owner, Jeffrey Jah — whose table he was seated at — for not keeping a closer eye on Casiraghi and company because he was aware of their “violent, belligerent and disruptive tendencies.” Hock says he shouldn’t be liable, and wants unspecified money damages for the injuries he says he suffered. Jah’s arguing in court papers he shouldn’t be held liable either. “We look forward to our opportunity to be heard in court,” said Hock’s lawyer, David Motola.