A trigger blocking device comprised of a frame removably affixed around a trigger guard of a rifle. The trigger blocking device holds a blocking shaft behind the trigger, the shaft being capable of sliding longitudinally or axially into two separate positions, one position where the shaft blocks the operation of the trigger and the other position where a recessed area in the shaft forms a trigger channel, when moved into position, allows the operation of the trigger. The blocking shaft extends across the frame and is positioned behind the trigger. When the blocking shaft is behind the trigger in a first position with the trigger channel not aligned with the trigger, the blocking shaft prevents rearward movement of the trigger, preventing the firearm from firing. When the blocking shaft is moved to a second position wherein the trigger channel is aligned with the trigger, the trigger when pulled can move rearward into the trigger channel to allow the firing mechanism of the firearm to be activated, that is, to fire.