Making that case is an advocacy group called the Nonhuman Rights Project. Since 2013, the group has filed lawsuits on behalf of four captive chimpanzees in New York and, in neighboring Connecticut, three elephants used in a traveling circus. They’ve lost those cases, but they have persuaded judges to take them seriously, and in October petitioned a New York state court to order Happy’s release. She wouldn’t be returned to the wild, but would be transferred to a sanctuary in California with more space and the company of other elephants. The hearing took place earlier this month, and while no decision was reached—the case will likely be moved to a court within the Bronx Zoo’s jurisdiction—it was still a unique moment to reflect on the status of animals and the law.

Until recently, the idea of elephant personhood would have struck legal observers as a joke. Just a few decades ago, most states still treated animal cruelty as a misdemeanor, like public intoxication or driving without insurance. But an increasing number of Americans take animal well-being seriously: A 2015 Gallup poll found that a majority “are very or somewhat concerned” about animal mistreatment. The legal system has changed in turn. Every state now considers animal cruelty a felony, and laws such as California’s recently passed Proposition 12, which improves living standards for farm animals, are becoming commonplace.

Still, these laws have blind spots and inconsistencies. The federal Animal Welfare Act exempts farm animals and most lab animals; the Humane Slaughter Act omits poultry. State laws are an inconsistently enforced patchwork, and practices that many people consider cruel—such as gestation crates for pigs—remain legal in many places. Even the most beloved animals don’t always receive much consideration. “In the vast majority of jurisdictions, if someone beats your dog to death in front of you, all you can sue them for is the cost of buying another dog,” says Chris Green, the executive director of Harvard Law School’s Animal Law and Policy Program.

Animal-welfare laws also depend on government intervention. Citizens can’t file suit on behalf of animals they don’t own. Animal-welfare laws fall short of actual rights—and centuries of legal custom have reserved rights for humans. “A thick and impenetrable legal wall has separated all human from all nonhuman animals,” writes Steven Wise, the Nonhuman Rights Project’s founder and lead attorney, in his book Rattling the Cage.

Read: Do we need zoos?

To help Happy breach it, Wise invokes both scientific research and legal principle. Elephants, attest scientists who filed affidavits in Happy’s case, are highly self-aware, are emotional, make choices, and have a rich sense of both past and future. (Happy, in fact, was the star of a landmark 2006 Science study describing how elephants can recognize themselves in mirrors, which is considered a measure of especially human-like awareness.) “Elephants share many key traits of autonomy with humans,” write evolutionary biologists Lucy Bates and Richard Byrne in their affidavit. Wise argues that respect for autonomy underlies our own legal right to physical liberty. Extending that to elephants is simply a matter of equality.

In a news release issued after this month’s hearing, the Wildlife Conservation Society—the Bronx Zoo’s owner—describes the lawsuit as “an academic exercise” that, in the words of the zoo’s director, Jim Breheny, is intended to “promote their radical philosophical view of ‘personhood.’” Happy’s present conditions, the society says, are perfectly suitable and meet established welfare standards, and moving her could be traumatic. (That issue won’t be adjudicated in this article; for more information, see court documents filed by Patrick Thomas, the Bronx Zoo’s associate director, and Joyce Poole, one of the biologists supporting the lawsuit.)