I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this is happening.
They're trespassing. It is illegal to build across someone's property line without their consent. You have the ability to file what's called an Action in Ejectment, asking a judge to order them to remove whatever encroaching structures they've built, at their own expense. They can also be ordered to pay you damages for trespassing on your land and pay the cost of restoring the land to the condition it would be in if they hadn't done this.
Some of them may try to tell you that, because they've been on your land for many years, it's too late for you to take action against them now. That is actually untrue in New York. The law legally presumes that a shed, fence, or other non-structural encroachment across a property line CANNOT gain title to the land. Neither can a person who mows or maintains across the property line. New York Real Property Actions Laws and Rules, Section 543.
These cases can be complicated, especially if you're suing several neighbors at once. It could help to have a local attorney draft and file the Complaint for you to get things moving.
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