A growing phalanx of lawyers is taking aim at Daimler Truck Holding AG and other major truck makers over a former price-fixing cartel. Observers say the sheer number of legal experts involved underscores the significant financial and reputational risks at play.

Recently enacted regulations by the U.S. Transportation Department have made it significantly tougher for non-U.S. citizens to secure commercial drivers’ licenses. The change follows a fatal crash in Florida that prompted renewed scrutiny of licensing requirements and highway safety.