This morning, an animal rights group known as the Nonhuman Rights Project (NhRP) filed a lawsuit in a New York Supreme Court in an attempt to get a judge to declare that chimpanzees are legal persons and should be freed from captivity. The suit is the first of three to be filed in three New York counties this week. They target two research chimps at Stony Brook University and two chimps on private property, and are the opening salvo in a coordinated effort to grant “legal personhood” to a variety of animals across the United States.

If NhRP is successful in New York, it could be a significant step toward upending millennia of law defining animals as property and could set off a “chain reaction” that could bleed over to other jurisdictions, says Richard Cupp, a law professor at Pepperdine University in Malibu, California, and a proponent of focusing on animal welfare rather than animal rights. “But if they lose it could be a significant step backward for the movement. They’re playing with fire.”

The litigation has been in the works since 2007, when animal rights attorney Steven Wise founded NhRP, an association of about 60 lawyers, scientists, and policy experts. The group argues that cognitively advanced animals like chimpanzees and dolphins are so self-aware that keeping them in captivity—whether a zoo or research laboratory—is tantamount to slavery. “It’s a terrible torture we inflict on them, and it has to stop,” Wise says. “And all of human law says the way things stop is when courts and legislatures recognize that the being imprisoned is a legal person.”

NhRP spent 5 years researching the best legal strategy—and best jurisdiction—for its first cases. The upshot: a total of three lawsuits to be filed in three New York trial courts this week on behalf of four resident chimpanzees. One, named Tommy, lives in Gloversville in a “used trailer lot … isolated in a cage in a dark shed,” according to an NhRP press release. Another, Kiko, resides in a cage on private property in Niagara Falls, the group says. The final two, Hercules and Leo, are research chimps at Stony Brook University. Wise says that 11 scientists have filed affidavits in support of the group’s claims; most of them, including Jane Goodall, have worked with nonhuman primates.

In each case, NhRP is petitioning judges with a writ of habeas corpus, which allows a person being held captive to have a say in court. In a famous 1772 case, an English judge allowed such a writ for a black slave named James Somerset, tacitly acknowledging that he was a person—not a piece of property—and subsequently freed him. The case helped spark the eventual abolition of slavery in England and the United States. Wise is hoping for something similar for the captive chimps. If his group wins any of the current cases, it will ask that the animals be transferred to a chimpanzee sanctuary in Florida. Any loss, he says, will immediately be appealed.

Regardless of what happens, NhRP is already preparing litigation for other states, and not all of it involves chimpanzees. “Gorillas, orangutans, elephants, whales, dolphins—any animal that has these sorts of cognitive capabilities, we would be comfortable bringing suit on behalf of,” Wise says. Some would be research animals; others would be creatures that simply live in confined spaces, such as zoos and aquariums. “No matter how these first cases turn out, we’re going to move onto other cases, other states, other species of animals,” he says. “We’re going to file as many lawsuits as we can over the next 10 or 20 years.”

Frankie Trull, the president of the National Association for Biomedical Research in Washington, D.C., says her organization will fight any attempts at personhood in the courts. Chimpanzees, she notes, are important models for behavioral research, as well as for developing vaccines against viruses like hepatitis C. “Assigning rights to animals akin to what humans have would be chaotic for the research community.”

Anatomist Susan Larson, who studies the Stony Brook chimpanzees to shed light on the origin of bipedalism in humans, says she is "very shocked and upset" by the lawsuit. She says the chimps live in an indoor enclosure comprised of three rooms—“about the size of an average bedroom”—plus another room where they can climb, hang, and jump from ladders and tree trunks. “Everything I do with these animals I’ve done on myself,” she says. “I understand that animal rights activists don’t want these animals mistreated, but they’re hampering our ability to study them before they become extinct.”

The more immediate threat to Larson’s research isn’t NhRP, however—it is the National Institutes of Health (NIH). In June, NIH announced plans to retire all but 50 of its 360 research chimpanzees and phase out much of the chimp research it supports. The U.S. Fish and Wildlife Service, meanwhile, has recommended that captive chimps be listed as endangered, which would limit any research that isn’t in their best interest. “Soon, the type of work I do will no longer be possible,” Larson says. “They have effectively ended my research program.”

Stephen Ross, the director of the Lester E. Fisher Center for the Study and Conservation of Apes at the Lincoln Park Zoo in Chicago, Illinois, wonders if there’s a compromise. Ross, who has studied chimpanzees for more than 20 years and played a role in crafting NIH’s new policy, advocates ending private ownership of chimps and invasive research. All other chimpanzees, he says, whether located at zoos or universities, should live in large enclosures, with access to the outside, and in group sizes of at least seven individuals. “You don’t need personhood to do that,” he says. “I think we share a common philosophy,” he says of NhRP. “We want to make things better for chimps. We just disagree on how to get there.”

To participate in a live video chat on this topic, check out this week's ScienceLIVE: Should Animals be Granted Legal Rights?

A more detailed version of this story will appear in the 6 December issue of Science.

*Clarification, 2 December, 4 p.m.: This item has been updated to reflect Richard Cupp's position on animal rights.