Safiel:
There is only one law breaker in this situation and that is the homeowner.
He placed an encroachment in a right of way. (in this case a civil violation)
He attached a booby trap with the intent to injure. (this could be misdemeanor or felonious assault depending on the State)
The public worker lawfully removed an encroachment from a public right of way and was injured by the booby trap.
The homeowner should be tried for his criminal actions and sued by the city to recover workman’s compensation costs, plus the cost of any time off from work needed by the worker to recover. Additionally, punitive civil costs should be awarded from the homeowner directly to the worker for his pain and suffering.
The homeowner should learn the boundary between his private property and the public right of way and keep his signs on his private property.
Looked it up to see if the municipality had anything in writing. They do.
Commerce Township Zoning Ordinance Article 30 Signs
SECTION 30.08. SIGN REMOVAL BY TOWNSHIP ACTION.
E. Temporary Signs.
Temporary signs affixed within a road right-of-way or corner clearance area, without a valid permit, or after permit expiration may be removed by the Township without notice. Signs removed shall be discarded.
http://commercetwp.com/download/33/zoning-ordinance-3-000/1994/article-30-signs-12-25-2013-2-24-2016.pdf
