Truck Manufacturers Sue CARB Over Zero-Emission Rules

Four major truck manufacturers Daimler Truck North America, International Motors, Paccar, and Volvo Group North America, have filed a federal lawsuit against the California Air Resources Board (CARB) over the state’s zero-emission vehicle (ZEV) requirements.

The companies argue they are caught between conflicting directives from California and the federal government. California insists on enforcing its 2023 Clean Truck Partnership agreement, while federal authorities have deemed those standards preempted by national law.

The 2023 Clean Truck Partnership and Its Requirements

The Clean Truck Partnership, signed in 2023, called for:

• Phasing out legacy diesel engine production from 2024–2026.
• Imposing increasingly stringent restrictions each year.
• Allowing some flexibility in how OEMs transition to ZEVs.

A key provision required OEMs to comply with CARB’s standards “irrespective of the outcome of any litigation” challenging the state’s authority.

California ultimately aims for 100% ZEV sales of heavy-duty trucks by 2045 where feasible.

Federal Rollback Creates Legal Conflict

In June 2025, Congress passed a joint resolution rolling back an Environmental Protection Agency policy that previously allowed California to set stricter emissions standards.

Since then:

• California has warned OEMs they could face civil penalties, exclusion from the state market, and loss of incentives if they fail to meet CARB rules.
• The U.S. Justice Department has issued cease-and-desist letters to CARB, stating that its enforcement contradicts federal law.

The OEMs argue that this “impossible position” requires judicial intervention to clarify which standards apply.

Legal Objectives of the Lawsuit

The manufacturers are seeking:

• A declaration that federal law supersedes CARB’s ZEV mandates.
• A judgment that the Clean Truck Partnership is unconstitutional.
• Confirmation that CARB’s rules violate the federal Clean Air Act.

The suit emphasizes the urgency of resolving the matter ahead of Model Year 2026, as OEMs must determine which trucks can be sold in specific markets well before production starts on January 1.

The Big Picture

This case adds fuel to the fire in the ongoing battle between state and federal authorities over emissions regulation, a conflict that directly impacts production timelines, compliance costs, and the pace of the zero-emission transition in the trucking industry.

If the court sides with the OEMs, California’s ability to enforce independent ZEV mandates could be significantly curtailed. If not, manufacturers may need to design vehicles that meet California-specific standards while also serving broader U.S. markets.

Source: TruckingDive