A New York City judge has heard arguments over the rights of two chimpanzees that advocates hope to free from a state university where they are kept.

Manhattan Supreme Court judge Barbara Jaffe did not make a ruling on Leo and Hercules' fate. But she did entertain nearly two hours of exchanges between a lawyer for the Nonhuman Rights Project and an assistant state attorney general.

Much of the hearing centred on the interpretation of centuries-old legal principles. The chimps did not attend.

A lawyer hoping to free the chimps said they are "autonomous and self-determining beings", should be granted a writ of habeas corpus and be moved from Stony Brook University to a sanctuary in Florida.

A government lawyer said the case should be dismissed because, among other arguments, the venue is not proper.

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