In a blender or food processor fitted with the metal blade, combine the orange juice, vinegar, chipotle chilies, salt, and sugar and blend until chilies are finely chopped. With the motor running, add the oil in a steady stream and blend until incorporated. Adjust seasonings, add the mint and set aside. The vinaigrette can be refrigerated overnight without the mint, which should be added just before serving.
Heat a grill. Brush fillets with olive oil and sprinkle with salt and pepper. Grill until cooked through, 3 to 4 minutes per side. To serve, transfer snapper fillets to a serving platter or individual plates and drizzle with the orange chipotle vinaigrette.