The landmark ruling, which threw into doubt the constitutional plausibility of Texas food defamation laws, was a severe setback for the cattlemen's case against the TV talk-show queen.
They are suing Ms Winfrey, the world's highest paid entertainer, for a remark she made on air in April 1996 about the possible threat of mad cow disease reaching American shores.
During an interview with an anti-meat campaigner, Ms Winfrey exclaimed: "It has just stopped me cold from eating another burger! I'm stopped!"
The following day cattle future prices in the Chicago market fell by 10 per cent. The plaintiffs in the case, clearly in awe at La Winfrey's power, said this was no coincidence.
Their case, which is being heard in the Texas pan-handle town of Amarillo, rested in large measure on a state law which holds that a hamburger, a sirloin cut, a pork chop, an orange, or a cup of coffee are sensitive, if not sentient, entities that deserve the same legal protection from libel as human beings.
Judge Mary Lou Robinson begged to differ, and the plaintiffs now have a much harder case to prove.Reuse content