Not sure about breaking the LAW but they are definately breaking a contract.
If you have all receipts of paymenst and written agreement it is possible to bring the person or establishment to a small claims civil court.
However It's not a simple or speedy process and not really something to waste precious time on during your vacation.
I would advise writting to the Jamaican tourist board.
http://www.visitjamaica.com/Default2.aspx
and the Negril chamber of commerce
http://www.negrilchamberofcommerce.com/
I would not be happy with someone forcing their decision on me as to where I would be staying.
B