The trigger guards being a 'natural' material, horn in this instance, glue up extremely well with 'super glue'.
The parts have to be clean as always, but the stuff will glue horn, leather, your fingers, ect together with excl results.

The Walther SxS shotguns used Bakelite or similar plastic material for their trigger guards and safety buttons.
Those have a strip of steel reinforcement inside the triggerguard casting but they still crack. Probably more from age than anything else.