A Footpath in England, Torn Down, Keeps Being Rebuilt by 'Fairies'

Demolishing these structures is simply unnecessary. Just put a sign up that says that, by crossing the bridge, you're responsible for any harm to yourself or others.

In Portugal, for example, there are plenty of old structures, like medieval walls, where it'd be destructive to install railings. A sign is simply put up to warn people that it might not be safe, and they are responsible for damages caused.