One of the traders bought two new X5 SUVs and an M3 model, then resold them at a 5,000 euros profit to buyers in Italy and Taiwan.
BMW says such unauthorized trading damages the company's exclusive marketing network.
"The existence of our selective dealer system is at risk," says Kathrin Stolz, from BMW's legal affairs department.
BMW is asking a German court to impose fines of up to 500,000 euros on the unauthorized traders to deter other buyers from profiting from the lack of availability of top range models in markets outside Germany.
BMW's sales contracts prohibit new car buyers from selling their vehicle until they have owned it for more than four months.
Cologne lawyer Christian Genzow says the contracts are unenforceable. "I don't know of any other concern that would dare to have such a condition in a contract," he says.
Genzow is defending the two traders taken to court by the Bavarian automaker.
Genzow says neither Mercedes nor Audi have conditions in their sales contracts banning buyers from reselling their new cars.
He adds that in May 2002 the Hamburg district court refused Ferrari the right to have a similar clause in its contracts.