With tentacles in Europe, the Americas and Asia, the Rathkeale Rovers have amassed incredible wealth from the banned trade.
In Europe alone they have been behind more than 60 documented thefts, valued at over €40 million.
Based around an extensive network of Traveller families, the Rathkeale Rovers are a top target of customs, wildlife and organised crime agencies in Europe and the US.
European agencies have hit members of the network with a total of €9m in tax demands.
This is part of a massive operation, codenamed Oakleaf, which spreads across more than 16 European countries in addition to the US.
Named after the town in Co Limerick, the Rathkeale Rovers were behind the theft of eight rhino horns, valued at €500,000, from the National History Museum warehouse in Swords, north Dublin, last April.
Rhinos have been hunted to the brink of extinction and traffic in rhino products is regulated by the Convention on International Trade in Endangered Species (CITES).
The rhino horns are mainly sold in China, where they are used for traditional medicine, as an aphrodisiac and a decoration in luxury products. Rhino horns can sell for, on average, €60,000 each, but often fetch a lot more.
Revenue has authority to take action if there is evidence that the goods are illegally imported into the State. Under the Wildlife Act 1976, the National Parks and Wildlife Service enforces regulations regarding the possession, use and trade of CITES listed species within Ireland.
Last September, the Criminal Assets Bureau led six searches in Limerick and Cork targeting members of the Rathkeale Rovers.
The searches of five homes and one office, located in Rathkeale and Raheen areas of Limerick and Newmarket in north Cork, were conducted to establish if properties and other assets can be confiscated under Proceeds of Crime laws.
There have been more than 50 arrests across Europe under Operation Oakleaf since it began in Nov 2010.
The operation was established by Europol, the EU police agency, on the request of gardaí.
Europol was described the network as a “mobile organised crime group”, which has set up companies all over Europe to legitimise their illegal activities and has laundered their income through properties and luxury cars.
Gardaí said the Rathkeale Rovers are involved in extensive criminality, which also includes labour exploitation, counterfeiting fraud, tarmac scams and tobacco smuggling.