Well, he should be careful because someone could successfully press charges if the device actually hurt someone. He should probably check with his attorney if a warning sign would suffice to protect him from a lawsuit.
Warning
Do not Touch Signs
Electrified
And a lightning bolt symbol
He’s covered.
You are correct, that is why you mix ghost pepper powder in some water and spray it on the signs where they are likely to grab them. :) I can attest to the completed transaction. :)