The contractual ownership of the Egyptian forward has become a complicated matter this summer, with the Viola embroiled in a bitter battle with the player and his agent.
Fiorentina are looking to secure Salah on a permanent basis after last season's impressive loan from Chelsea, but he refused to turn up to training and his agent said he would not be returning to the Artemio Franchi.
Della Valle had already claimed that "lawyers will solve" the debate about who owns Salah's rights following confirmation from the Serie A side that they would be suing the 24-year-old for breach of contract.
Jose Mourinho has stated there's no way Salah is staying at Stamford Bridge and Roma have emerged as the frontrunners to sign him, though Della Valle was keen to stress he's still a Fiorentina player.
"We have a contract in our possession that we will exercise," the Fiorentina chief told Corriere dello Sport when asked about Salah joining another club. "The player was persuaded into agreeing to this action by his agent."
Della Valle also commented on the lack of transfer arrivals this summer for Paulo Sousa's men, who defeated Barcelona 2-1 on Sunday thanks to early efforts from Federico Bernardeschi.
"Soon all the scepticism will go away," he added. "I am convinced this new era with Sousa after sacking Vincenzo Montella will be a success. The transfer window runs until August 31, there's time.
"I ask fans to continue to believe in me. When you swap coaches, it's normal to have a few weeks of adaptation. All around us are teams awash with money, too."
Referencing Bee Taechaubol's purchase of 48 per cent of AC Milan, Della Valle added: "The big teams have all strengthened and I'm happy for Silvio Berlusconi as it'll be a lot easier for Milan to navigate the market with an extra €400 million."