People for the Ethical Treatment of Animals (PETA) are suing the aquatic theme park chain under the 13th Amendment of the US Constitution, which abolished slavery.

Ingrid Newkirk, president of PETA said: “All five of these orcas were violently seized from the ocean and taken from their families as babies.

“They are denied freedom and everything else that is natural and important to them while kept in small concrete tanks and reduced to performing stupid tricks.”

The lawsuit, which was filed on Tuesday in US District Court in San Diego, says SeaWorld violated the rights of five performing orcas at parks in California and Florida.

The biggest issue in the case is whether an animal can sue for violation of constitutional rights.

The 13th Amendment outlaws slavery and “involuntary servitude” in the US, without a specific reference that it only applies to humans.

It says: “Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.”

Sea World in San Diego responded saying PETA’s attempt to “extend the Thirteenth Amendment’s solemn protections beyond human beings is baseless and in many ways offensive.”