Battles over California’s Advanced Clean Trucks rule rage far beyond state line

With slightly tightened restrictions under the California Advanced Clean Trucks (ACT) rule having gone into effect at the start of 2025 and the prospect of numerous states following the Golden State’s lead, the regulatory world has been awash in dueling communications on the subject.

On a microeconomic level, the ACT has led to the halting of some truck sales in Oregon. But a bigger battle is taking shape across multiple states.

Unlike its sister regulation, the Advanced Clean Fleets (ACF) rule, ACT has the waiver from the Environmental Protection Agency that it needs to be implemented in California. The rule provides a combination of carrots and sticks to move OEMs toward producing more zero-emission vehicles (ZEVs) to be sold into California.

The ACF – which awaits a decision on its own waiver request from EPA, expected in the remaining days before the end of the Biden administration – is a similar set of runways and regulations to move the state’s truck fleet toward ZEVs. But the ACF is targeted at vehicle buyers, not manufacturers.

The ACT technically went into effect on Jan. 1, 2024. But enforcement was put on hold while the waiver request made its way through the EPA.

The degree of attention that the ACT has been getting nationally stems from the numerous states that have decided to follow California’s lead – and the problems that critics argue those decisions could cause.

Long before the introduction of ACT and ACF, California’s more stringent rules on vehicles and its gigantic population created concern among automakers and engine manufacturers about the “two-car” problem: An OEM would have to make one type of vehicle to meet California’s standards and one with lower environmental standards for the other 49 states. The default choice becomes making a car for California standards, and the rest of the country ends up following along.

That reality is why states regularly challenge waivers on rules granted by the EPA to California, even though ostensibly a state regulation shouldn’t impact other states. So far, California has prevailed in legal battles regarding the waivers and the right to adopt its own rules. 

The story on how various factions are lining up over the ACT can be told to some degree by the missives that have been flying in recent weeks, along with a lawsuit. Here are some of the communications that have been sent on the issue.

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