neighbor hung a “smile you’re on camera” sign on my fence pointing into my backyard

r/legaladvice thinks I’m trolling, which I am not

My neighbor and I do not get along. He seems to harbor a lot of resentment towards us because we erected an off-the-shelf gazebo in our backyard that he tried to ding us on, but the city approved it after multiple inspections.

In the latest tit for tat, he hung a sign on our fence pointing into our backyard saying “smile you’re on camera.” And I don’t see a visible camera. Is that legal at all? Does it count as harassment?

So far my only response has been to go shirtless and temporarily park yard waste (green bin that won’t fit) in that general vicinity (about 10 feet away). I hope he enjoys going through the footage of a total dad bod show, man boobs and all. I might order a speedo.