Chimpanzees being kept at a New York university are not people and so are not being unlawfully detained, a judge has ruled.
The Nonhuman Rights Project (NhRP) brought the case, arguing that the animals have a right not to be “imprisoned”.
Justice Barbara Jaffe rejected the claims – but said such a move could be possible in the future.
The office of New York state Attorney General, which was defending against the animal rights group, said the case was “a radical attempt to blur the legal boundaries that exist between humans and animals”.
Stony Brook University in Long Island has kept the chimpanzees for research since 2010 and said it was analysing the “thoughtful” decision.
The NhRP, which has taken a number of other similar cases in recent years, said it would appeal.
In her ruling, Justice Jaffe said that previous mistreatment of people, “whether slaves, women, indigenous people or others, as property” is not a reason for extending human rights to animals.
However, she also said that efforts to extend legal rights to chimpanzees “may even succeed” one day.
The campaign group said it would soon be pursuing a case involving elephants.
NhRP’s case focused on attaining a writ of habeas corpus – a concept which was developed from Magna Carta and can be demanded if someone believes they are being unlawfully detained.
In May the office of the New York Attorney General said: “Any such extension of the writ could set a precedent for the release of other animals held in captivity, whether housed at a zoo, in an educational institution, on a farm, or owned as a domesticated pet, and enmesh New York courts in continuing litigation”.