A state judge in New York has dealt the latest blow to an animal rights group’s attempt to have chimpanzees declared “legal persons.” In a decision handed down this morning, New York Supreme Court Justice Barbara Jaffe ruled that two research chimps at Stony Brook University are not covered by a writ of habeas corpus, which typically allows human prisoners to challenge their detention. The Nonhuman Rights Project (NhRP), which brought the lawsuit in an attempt to free the primates, has vowed to appeal.

“The decision … was correct, not only because it followed existing precedent, but because the entire project of seeking to confer legal rights on animals is misguided from the ground up,” writes Richard Epstein, a legal scholar at New York University (NYU) in New York City, in an email to ScienceInsider. But NhRP President Steven Wise says he is encouraged by the judge’s wording, noting that Jaffe wrote that legal personhood isn’t necessarily restricted to human beings and that “efforts to extend legal rights to chimpanzees are thus understandable” and may someday even succeed. “Justice Jaffe's decision is another large step towards attaining legal personhood for chimpanzees,” Wise writes in an email. “We will be quoting from her opinion for years.”

The case started as started as a series of lawsuits filed by NhRP in December 2013. The group claimed that four New York chimpanzees—Hercules and Leo at Stony Brook and Tommy and Kiko on private property—were too cognitively and emotionally complex to be held in captivity and should be moved to a sanctuary. NhRP lost all of these cases and began appealing them. This past April, the group scored its first major victory when Jaffe ruled that Stony Brook had to come to court and defend its possession of Hercules and Leo. That happened late this past May, with Wise squaring off against Christopher Coulston, an assistant state attorney general representing the university.

In today’s ruling, Jaffe seems to express some sympathy for NhRP’s arguments. She writes, for example, that something does not have to be a human being to be treated like a person in the eyes of the law, noting that corporations have been considered legal persons in some cases. She also states that the concept of legal personhood continues to evolve: “Not very long ago, only Caucasian male, property-owning citizens were entitled to the full panoply of legal rights under the United States Constitution.” And in her conclusion, she quotes Supreme Court Justice Anthony Kennedy’s words from a 2003 gay rights case: “Times can blind us to certain truths and later generations can see that laws once thought necessary and proper in fact serve only to oppress.”

But ultimately, Jaffe writes that she is bound by legal precedent—specifically a decision made by a higher court last December in the earlier case involving the privately owned chimpanzee named Tommy. That court ruled that chimpanzees aren’t entitled to the same legal status as human beings, and that they don’t meet the legal definition of “person.”

“Even were I not bound by [that case],” Jaffe writes, “the issue of a chimpanzee’s right to invoke the writ of habeas corpus is best decided, if not by the Legislature, then by the Court of Appeals, given its role in setting state policy.”

That’s not to say that chimpanzees should be treated like inanimate objects, NYU’s Epstein says. “Of course animals are not things, but they are not human beings either,” he writes. “The Nonhuman Rights Project is in my view a diversion from the central question of what form of protections should be afforded by people to animals and why.”

Susan Larson, the anatomist who studies Hercules and Leo at Stony Brook, says the chimps—which technically belong to the New Iberia Research Center in Louisiana—will likely be leaving the university in the near future, either to go to a sanctuary or back to New Iberia.

Wise says his group is filing an immediate appeal as well as focusing on new cases. “We are deep into planning our next lawsuit, which will be on behalf of elephants in another state,” he writes. “We expect to file it this year.”