That is tough. On the good side, he isn’t seeking problems by reporting your building. Maybe he’s more of a “live, let live” mindset. Still annoying to have his chickens negatively impacting your grass, and poop on cars.
Why do they prefer your yard? More to forage? Other chickens? Sunnier?
Can you post any pics of the area in question? Maybe more suggestions when we know what your dealing with based on terrain/etc.
Putting up a fence/netting may not do much, particularly with game hens. Electric fence is a possibility - as long as legal in your area. However, Chickens tend to fly up to a thing then onto something else, so up to a fence, down to the ground. Or up to the fence, then up to a branch, etc. so, an electric fence may not do much bc they won’t be touching the ground or ground wire. Some people say a flimsy top string can work- it is too flimsy for the bird to perch on before they go to the next “thing”.