I’ve read that, long ago, one of the punishments for pickpockets was to nail their ear to a pillory and leave them there to be heckled. The only way to free themselves was to rip their ear from the nail - which they’d eventually do, once they become desperate enough. Seems like we could apply a similar technique here. We wouldn’t even need nails since they’ve essentially nailed their ears themselves.
You could speed up the self-removal process by setting vicious dogs on them, or maybe a judicious application of fire ants would be better.