This week, a New York judge granted two chimpanzees, Hercules and Leo of Stony Brook University, the right to have their day in court.

Back in December 2013, the Nonhuman Rights Project (NhRP) filed a suite of lawsuits claiming that the pair of lab animals, together with another two living on private property, were too intelligent, self-aware, and emotionally complex to be detained in captivity, and that they should be relocated to a chimpanzee sanctuary called Save the Chimps in Fort Pierce, Florida. The group petitioned multiple judges with a writ of habeas corpus—traditionally used to prevent people from being unlawfully imprisoned—but each case was struck down, Science reports.

On Monday, in the organization’s first major victory, New York Supreme Court Justice Barbara Jaffe signed an order requiring Stony Brook representatives to appear in a court hearing on May 27 to respond to NhRP’s claim that the two chimps are being unlawfully detained. A judicial action could force the university to release the chimps. And since a habeas corpus can only be granted to a person, this order implicitly suggests that these chimps are being recognized as “legal persons”—but you might be reading into it too much, some say.

“This is a big step forward to getting what we are ultimately seeking: the right to bodily liberty for chimpanzees and other cognitively complex animals,” NhRP’s Natalie Prosin tells Science. “We got our foot in the door. And no matter what happens, that door can never be completely shut again.” A positive ruling would be the first time in any state that a non-human animal had been granted rights previously reserved for Homo sapiens, Nature explains. But even if NhRP loses the case, the habeas corpus ruling “strengthens our argument that these nonhuman animals are not property,” Prosin adds.

However, the judge amended the court order on April 21, and the words “writ of habeas corpus” have since been struck out. That means the court hasn’t decided whether the two chimps are to be treated as legal persons. Courts don’t have to make a determination about legal personhood before giving opponents the chance to respond. But as Nature describes it, the judge inadvertently opened a constitutional can of worms only to clamp it shut a day later.

A Stony Brook spokeswoman would only comment that the university “awaits the court’s full consideration on this matter,” according to The New York Times. The burden of proof is on New York attorney general Eric Schneiderman, charged with representing the school, to argue that the chimps aren’t persons.

Both Hercules and Leo have been used in biomechanics research to understand the evolution of human bipedalism.

[Via Science, Nature]