Minneapolis- A college professor pleaded guilty on Wednesday to illegally smuggling items made of elephant ivory and agreed to pay a $500 000 fine that prosecutors say should be a deterrent to such activity.Yiwei Zheng, a philosophy professor at St Cloud State University, acknowledged smuggling ivory carvings of potted flowers and other items from the US to China in April 2011. He also admitted to illegally exporting two rhinoceros horns to China in July 2010 in violation of the US Lacey Act, which bans trade in wildlife that has been illegally taken, transported or sold.In addition to the steep fine, the 43-year-old could face about three years in prison when sentenced in May. A federal judge will make the final decision on the fine and sentence.Assistant US Attorney Laura Provinzino said that when ivory and rhinoceros horns enter the market, it fuels demand for the products and leads to poaching of critically endangered animals."We want to make sure people know they can't profit from this," Provinzino said after Wednesday's hearing in federal court in Minneapolis.Zheng's attorney, Tim Webb, said his client has long traded in historical Chinese artifacts and authored books on Chinese trinkets. Webb said most of the items Zheng had were antiques and weren't illegal in and of themselves, but that Zheng knowingly didn't follow regulatory and permitting requirements to buy and transport some items. Webb said his client is remorseful and regrets his actions.Zheng would not have been granted a permit if he would have applied for one, according to Pat Lund, resident agent in charge of the US Fish and Wildlife office in Minnesota. The ivory items were seized by Fish and Wildlife inspectors in Chicago, and several more were seized during a search of Zheng's home.Zheng, who has taught at St Cloud State since 1999, was indicted last year on several charges, including conspiracy. He has been free on bond and has continued to teach at the university in St Cloud, about 60 miles northwest of Minneapolis.All rhinoceros and elephant species are protected, and trade in rhinoceros horn and elephant ivory has been regulated by an international treaty since 1976, according to the indictment. Any animal species listed as protected under the treaty cannot be legally exported from the US without approval from the US Fish and Wildlife Service and proper permits.Demand for items made of rhinoceros horn, such as libation cups, has resulted in a thriving black market and has pushed most species of rhinoceros to the brink of extinction, the indictment said. Elephants are also endangered or threatened because of the demand for ivory.Prosecutors said the ivory and rhinoceros-horn items documented in Zheng's case had a fair market value of between $550 000 and $1.5m.