The argument has been that scientists have found that a chimp is cognitively similar to humans, therefore deserves some of the same rights. In this case, the Nonhuman Rights Project is asking the court for a writ of habeas corpus, which compels a person's captor to explain why he has a right to hold a person captive.
The lower court that first heard this case threw it out.
The judge in the case said he agreed with their arguments but did not agree that New York's habeas corpus law applied to a chimp.
The New York Supreme Court Appellate Division, Third Department, which heard arguments today, has signaled it is taking this case seriously.
Earlier this year, it issued a preliminary injunction preventing Tommy from being moved outside the state.
It's unclear when this court will issue its decision, but these kind of changes in the interpretation of law are usually handed down by higher courts.