To add to what Tyman1876 said, here is the link. http://www.dec.ny.gov/docs/wildlife_pdf/ask.pdf
Also have them check into the General obligation laws, or better yet provide them some info on it.
from the DEC: http://www.dec.ny.gov/outdoor/8371.html
Q. Is posting required to protect landowners from liability?
A. No. Whether the property is posted or not, the General Obligations Law protects landowners from liability for non-paying recreationalists on their property. Because of this protection, recreational liability lawsuits against rural landowners are uncommon. Recreational activities covered include: hunting; fishing; organized gleaning (picking); canoeing; boating; trapping; hiking; cross-country skiing; tobogganing; sledding; speleological (caving) activities; horseback riding; bicycle riding; hang gliding; motorized vehicle operation for recreation; snowmobiling; non-commercial wood cutting or gathering; and dog training. This protection does not apply in cases of willful or malicious failure to guard or warn against dangers.