William, founder of United for Wildlife, called it a "significant victory" after US District Judge Gregory H Woods sentenced Moazu Kromah to more than five years in prison.
Kromah was sentenced on Thursday for conspiring to traffic parts from the endangered species, which involved the illegal poaching of more than 35 rhinoceros and more than 100 elephants.
The 49-year-old, from Kampala in Uganda, previously pleaded guilty on March 30 to one count of conspiracy to commit wildlife trafficking and two counts of wildlife trafficking.
He and two co-conspirators were part of a criminal gang based in Uganda and surrounding countries which engaged in the large-scale trafficking and smuggling of rhinoceros horns and elephant ivory, court documents said.
From about December 2012 to about May 2019, they conspired to transport, distribute, sell and smuggle, at least 190 kilograms of rhinoceros horns and 10 tonnes of elephant ivory.
The estimated average retail value of the rhinoceros horn and elephant ivory involved in the scheme is valued at about $US7.4 million ($A10.7 million), court papers state.
The contraband came from or involved various countries in East Africa, for buyers in the United States and countries in Southeast Asia.
Kromah was extradited to the United States from Uganda on June 13, 2019 to face the charges.
"Today's sentencing demonstrates both what is possible when a co-ordinated international response is brought to bear against the illegal wildlife trade, and why it is essential," Prince William said.Â
"This is a significant victory and a landmark case.
"It is further proof that we have the tools to combat this insidious crime and is testament to the power of international collaboration.
"I'd like to congratulate everyone involved for their meticulous planning and determination to pursue justice.
"Thanks to their perseverance, hundreds of endangered animals and the communities that live alongside them have been protected, sending the strongest possible message that together we can defeat the illegal wildlife trade."
In imposing his sentence, Judge Woods remarked that a significant sentence was necessary to send a "loud and clear message" that such large-scale wildlife trafficking warrants serious consequences.
The collaboration of a variety of organisations in different countries, from law enforcement agencies and governments to NGOs and private sector organisations, helped bring Kromah to justice.
That includes partners of United for Wildlife (UfW), an initiative founded by Prince William and The Royal Foundation, Kensington Palace said.
Since 2016, UfW has brought together more than 250 law enforcement and other government agencies, conservation NGOs, transport companies and financial institutions to combat the illegal wildlife trade.
