This follows a decision by a Cologne tribunal banning state lottery Westlotto affiliates from accepting heavy bets from people they know to be living on social security or unemployment benefits.
The court backed a March ruling which said Westlotto should refuse to take sporting bets from punters "who bet money far in excess of their revenues," especially those receiving minimum social security benefits.
The court was not immediately available to explain what was meant by a heavy bet, or how Westlotto employees could know which punter was on the dole.
In March, the court had ruled that employees were not required to check the worth of customers.
A spokesman for Westlotto, Axel Webber, said the court's decision "is and remains out of touch with reality", adding that his firm would appeal the ruling.
"To refuse to take a bet simply because of a suspicion would amount to discrimination, according to our reading of the law," Webber said in a statement.