Irish defendants were among nine alleged members of an international network of rhino horn and ivory traffickers who went on trial in France on Monday.
The investigation into the alleged smuggling began in 2015 when police discovered several elephant tusks and €32,800 in cash in a BMW during a random traffic search, according to wire service AFP.
It is alleged the Irish occupants of the car were members of the Limerick-based gang the Rathkeale Rovers, who told police they were antique dealers.
Police later discovered workshops for turning rhino horns and elephant tusks into powder for export as well as one rhino horn weighing nearly 15kg, according to newspaper Le Monde.
Other defendants on trial in Rennes include alleged traders from China and Vietnam, according to AFP, which says two of the defendants are on the run. They could face sentences of up to 10 years and heavy fines if convicted.
According to environmental group the Robin de Bois association, at the time of the alleged events, the retail value of a kilogramme of ivory on the Asian market was $5000 (€4,200) while a kilogramme of Rhino horn was $1,000 per gramme. The hearing is due to continue until Wednesday.