NYTの記事だと

　⇒Japan Again Suspends Shipments of Beef From U.S. - New York Times

Mr. Boyle said Japanese safety standards were tougher than the standards used by the rest of the world.
　
"The Japanese perceive the boneless product as being safer than bone-in product," he said. "Clearly, according to international safety standards, both products are safe."
　
Atlantic Veal and Lamb characterized the shipment as an honest mistake and said the piece of veal it shipped came from animals less than four and a half months old that had never tested positive for mad cow disease.
　
"We are absolutely confident that the product is safe," Philip Peerless, the president of the company, said in a statement. "However, we regret that there was a misinterpretation of the export requirements and an honest mistake involving a very small amount of product that has led to this degree of concern."

　ルール違反はルール違反なので、弁解の余地はないのだが……
　安全性の面では存外に問題のないしろものではあったのだろう。
　若干、シッピングの問題かなという印象もあるが。
　というか、日本基準に米国が慣れてないのかも。