Light Trespassing on your property?
Here's what you can do:
Talk to your neighbor about the benefits of dark skies and the harms of light pollution. Be friendly and work on understanding their lighting needs. Many people don't even know their choices are having a negative impact, and after hearing so, are willing to change.
Give us the offending property's address and types of lights causing the trespass so we can log your complaint and potentially reach out to them for a conversation.
Are there other neighbors who are also affected? Ask them for support. Having some kids on board can help too.
Determine what kind of lights and fixtures they are using and find alternatives with softer bulbs and better shielding. Offer to pay for the upgrades. If you make it easy for them they may be more likely to change.
Suggest timers / motion sensors.
Keep the dialogue open and be friendly. Try to understand why they need so much light. Usually there are better ways to get this need met that don't involve blasting the whole neighborhood with light.