HARTFORD (AP) — Advocates for human rights for animals lost another legal battle Friday in their efforts to free three elephants from a Connecticut petting zoo.

A three-judge panel of the Connecticut Appellate Court upheld a lower court and rejected an appeal by the Nonhuman Rights Project, which had filed a habeas corpus petition on behalf of the elephants.

The group, based in Coral Springs, Florida, alleged elephants Beulah, Minnie and Karen were being detained illegally in "deplorable" conditions at the Goshen-based Comerford Zoo and wanted them moved to a natural habitat sanctuary.

The judges determined the group did not have legal standing to sue on behalf of the elephants, who themselves would not have standing to sue because they're not human.

Judge Christine Keller wrote that allowing the elephants to use habeas corpus laws "would require us to upend this state's legal system to allow highly intelligent, if not all, nonhuman animals the right to bring suit in a court of law. At this juncture, we decline to make such sweeping pronouncements when there exists so little authority for doing so."

A spokeswoman for the Nonhuman Rights Project said members are reviewing the ruling before deciding whether to appeal to the state Supreme Court.

The Commerford Zoo has not responded to messages seeking comment and did not file briefs in the case.

Zoo owner Tim Commerford has previously defended how the zoo cares for the elephants, denied claims of mistreatment and said the elephants were like family.

The Nonhuman Rights Project has argued in the suit that elephants "are autonomous beings who live extraordinarily complex emotional, social, and intellectual lives and who possess those complex abilities sufficient for common law personhood and the common law right to bodily liberty."

When Superior Court Judge James Bentivegna dismissed the lawsuit in December 2017, he called the group's petition "wholly frivolous on its face in legal terms."