The Pennsylvania Motor Truck Association (PMTA) is applauding a major victory in Washington as the U.S. Senate voted to reject certain standards that the California Air Resources Board (CARB) had included in its Low NOx Omnibus rule, a sweeping emissions regulation that would have sharply increased the cost of new diesel trucks and disrupted fleet operations across Pennsylvania.

The 49-46 Senate vote follows action in the U.S. House to rescind the EPA waiver that had allowed California and ten other states to impose emissions rules far stricter than federal standards. It now heads to the President’s desk.

This Congressional Review Act (CRA) resolution invalidates the EPA’s 2024 decision to grant California authority to enforce the Low NOx rule. The rule that was set to take effect for MY 2027 trucks mandated a 90% reduction in NOx emissions.

In addition to blocking the Low NOx rule, Congress also passed a separate resolution under the Congressional Review Act to repeal the EPA waiver allowing California to enforce its Advanced Clean Trucks (ACT) regulation. While Pennsylvania has not adopted the ACT rule, it has been enacted in 11 states and was widely viewed as an attempt by California to set a national zero-emissions vehicle (ZEV) mandate for the trucking industry. The ACT rule would have required manufacturers to sell increasing percentages of electric and zero-emission trucks between 2024 and 2035—despite significant concerns about cost, infrastructure, and technology readiness. The repeal underscores a broader federal pushback against state-level rules that risk becoming national standards without Congressional oversight.

While these actions are welcome, they do not change the fact that California regulation will continue to bear significant consequences for Pennsylvania. That’s because the PA Department of Environmental Protection (DEP) adopts CARB’s regulations on a rolling basis—an issue which PMTA is actively litigating in the Commonwealth Court. That lawsuit argues that Pennsylvania cannot give regulatory authority to another state.

On May 10, 2025, DEP announced it is extending its suspension of enforcement of the Low NOx rule through January 2, 2028, citing pending litigation and federal action—now affirmed by this Senate vote.

“This vote validates what PMTA has been saying all along: these mandates are legally questionable, economically damaging, and completely disconnected from the operational realities of trucking,” said Rebecca Oyler, President and CEO of PMTA. “Congress has taken decisive action to stop California from setting de facto national policy on vehicle emissions.”