You could call this a case of the rhino's revenge.

On Tuesday morning, federal agents with the US Fish and Wildlife service entered a restaurant in St Cloud, Minnesota, and arrested Yiwei Zheng, 42, a philosophy professor at St Cloud State University.

Zheng, a naturalized US citizen who grew up in Shanghai, is being charged with smuggling elephant ivory and rhinoceros horn out of the US and into China from 2006 to at least 2011, the Minneapolis Star-Tribune reports.

His arrest follows the unsealing of an indictment alleging that he violated the Endangered Species Act and international treaties that protect endangered species.

In addition to his teaching career, Zheng has been operating an on-line sales business called "Crouching Dragon Antiques" out of his home in St Cloud since 2010.

According to the business' profile on Buzzfile, the operation "primarily operates in the Antiques business / industry within the Miscellaneous Retail sector. This organization has been operating for approximately 5 years. Crouching Dragon Antiques is estimated to generate $38,000 in annual revenues, and employs approximately 1 people at this single location."

That "one people" is Zheng and, according to the warrant, there are no records of Crouching Dragon Antiques ever getting an import-export license or declaring any wildlife specimens. The website offered wildlife specimen parts called "ox bone" for sale, which a federal search warrant suspected of being ivory.

According to the indictment, Zheng smuggled the ivory and horn for sale by co-conspirators, knowing it was illegal. He is also accused of participating in eBay auctions, mislabeling packages and failing to declare the items at Border Control and US Customs.

Zheng told special agents that he sold two rhinoceros horns to a Chinese national named Zhang at a McDonald's in St Cloud, but he had actually exported them to a co-conspirator in China, the indictment said.

Elephant ivory and rhino horn have been regulated globally since 1976, with 173 countries signing on to a treaty — Convention on International Trade in Endangered Species (CITES) — to protect endangered animals, fish and plants. The more ivory that is ceremoniously destroyed now and then, however, has only seemed to fuel the demand as well as the rampant poaching across Africa to meet that demand.

But it was a centuries old rhino horn that put the feds on Zheng's trail. In 2011, a FedEx Trade Networks unit alerted wildlife agents in Memphis, Tennessee, that Zheng had shipped a suspicious looking package to himself from France.

On inspection it was found to contain an intricately carved libation cup made from Javan rhino horn that Zheng had bought at Christie's in Paris. The feds confiscated it and started keeping an eye on Zheng.

Rhinos, which are native to Africa and Asia, are one of the most endangered species. Trade in their horns has been banned since CITES was enacted but antique crafted horn, that is anything made prior to 1947, is still fair game, although heavily regulated. It requires approval from the US Fish and Wildlife Service as well as permits depending on which category the species falls under, which apparently Zheng had not obtained.

Rhino horns have traditionally been carved into elaborate handles for daggers and canes in the Middle East, especially Yemen. The horn, which is made of keratin, the key structural component of hair and nails, is also prized for rumored medicinal properties, from aphrodisiac to a cure for cancer in some traditional Asian pharmacologies. Powdered rhino horn reportedly goes for about 48,000 euros ($51,561) per kilo in some places.

In China, rhino horns were carved into libation cups which still occasionally show up at auctions. In 2010, a 17th-century cup sold on the block at Christie's in Hong Kong for 2.5 million euros. In 2011, a 19th century rhino cup in the form of a lotus blossom went for 75,000 euros in Ireland.

According to the New York Times, illegal wildlife is one the world's largest markets in contraband, to the tune of $19 billion a year.

Zheng's indictment did not include the value of his imports and exports or his contribution to that total, but it's a good thing to put a dent — however little — in the ghastly industry.

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