Legal Question in Environmental Law in New York

Re: neighbor

Likely, very little. Generally, neighbors have little recourse when neighbors build within the limits of the local zoning laws. There might be another state or local statute somewhere that might upset the neighbor's new garage, but such an unlikely expectation would likely require hiring an attorney to carefully research the law for a new theory and new law which would force the razing of the garage. Nationally, new construction that has been built in violation of a law/code without prior variance has been known to come down--so it's not impossible but unlikely.

If you're serious about examining the issue futher, you should consult a local/area attorney who has dealt with similar issues before or you might be stuck with neighborly pursuasion to replant the trees.