PARIS — French communications group Havas and Swiss-based Richemont have formed a shareholders al-liance which effectively prevents corporate predators from making advances on pay TV giant Canal Plus.The shareholder pact, which replaces an earlier agreement between Havas, Generale des Eaux and Societe Gener-ale, gives Havas and Richemont a combined 49% stake in Canal Plus, which last week reported 1996 profits of $130 million. Current French legislation says that a single shareholder or shareholders acting together can have a maximum 49% stake in a private network. Richemont, which is about to sign off on the merger of Dutch-based NetHold with Canal Plus, picked up 15% of the Gallic paybox as part of that deal. Havas controls 34% following Generale des Eaux’s recent decision to exchange its shares in Canal Plus for a posi-tion as Havas’ main backer. This latest shareholder agreement, which runs for an initial three years, also sees Havas get seven boardroom seats, while Richemont takes three. In what was clearly designed as a comforting message to Canal Plus chairman Pierre Lescure, Havas and Richemont said that they want to maximize Canal Plus’ stock exchange value by maintaining the paybox’s mana-gerial independence. The last time this kind of shareholder agreement was put together, in April 1994, the then paybox chairman Andre Rousselet resigned in a fit of pique.