'Les Bleus' were awarded a penalty after Antoine Griezmann's corner from the right struck the arm of Ivan Perisic, despite the Croatian having his view blocked by Balise Matuidi.
The Argentine did not initally award the penalty, but after minutes of deliberation and a review on the pitch-side monitors he opted to reverse his decision.
Speaking to 'Sky Sports News', Gallagher expressed his fury at the decision, saying: "100 per cent not a penalty. He's far, far too close to the ball as it comes over the forward's head.
"It just strikes him - he doesn't move his hand to the ball, he's got no intention of handling the ball. The law says it has to be deliberate. His arms aren't in an unorthodox position - it just doesn't tick any boxes."
Griezmann coolly sent Danijel Subasic the wrong way from the spot to restore France's lead, with Didier Deschamps' side running out 4-2 winners.