Lest anyone else be tempted, booby-traps are outlawed in every
jurisdiction and have been since the Magna Carta. to the Pooh.

What's outlawed are "man traps" which are often called "infernal devices"
which KILL or seriously wound anyone who trips it.

An electric fence is FAR short of this. It's can't kill. It just
"shocks." It's quite acceptable to keep animals from "pushing" on a fence
and, indeed, have been used to keep dogs on the "right side" of a property
line.

Anyone who "electrifies" a political sign with an electric fence charger
would not be in violation of any serious state laws but might face multiple
convictions under local laws.

Off hand, I would say that "next time" folks will put up small warning signs
about the electric fence and a "token" electrified wire which is also
connected to the actual sign.

It's important, of course, that the fence charger be UL aproved and not be
capable of inflicting fatal shocks.

Slight OT: If memory serves, at least one small business owner has "gotten
away with murder" when he hooked up the 120 volts "mains" to a ceiling
entrance to his business. The bad guy was killed and the business owner
was let off by a jury.