Attorneys for the animal rights group People for the Ethical Treatment of Animals (PETA) filed a lawsuit in federal district court last week claiming that Sea World’s five killer whales are slaves and deserve legal protection. The “plaintiffs” are Tilikum and Katina in San Diego and Corky, Kasatka, and Ulises in Orlando.

“By any definition, these orcas are slaves,” Jeff Kerr, general counsel for PETA, was quoted as saying, “kidnapped from their homes, kept confined, denied everything that’s natural to them and forced to perform tricks for Sea World’s profit.”

The legal problem for Sea World, according to PETA, is the 13th Amendment to the U.S Constitution. Passed at the close of the Civil War as the first of the so-called “Reconstruction Amendments,” the 13th makes slavery illegal. Section 1 is clear about that:

“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.”

What the language is not so clear about is whether the prohibition against slavery only comes into play when you’re talking about humans. A common sense argument is that such a distinction shouldn’t be necessary. Applying the Constitution to whales or other animals sounds uncommonly silly and I can’t image that the possibility of such a thing happening ever occurred to the people who drafted the 13th Amendment.

Silly or not, however, PETA is arguing that the lack of specific restrictions in t