Wesley J. Smith has written about a case in Argentina in which an orangutan named Sandra has been declared by the court to be a non-human person. This ruling essentially would grant Sandra her freedom because it is unethical to hold people captive unlawfully.
The BBC has even written about litigation in the United States to try to get Tommy, a chimpanzee living in captivity, recognized as a "legal person."
Read the rest at the Life Training Institute blog.