Since the beginning of President Donald Trump’s second term, several environmental policies related to truck emissions have been modified or eliminated. These changes—especially those affecting Califo
ia, DEF systems, and DPF filters—have brought some relief to parts of the trucking industry, but they have also created a great deal of confusion among drivers.

Let’s clearly break down what is true, what is not, and what is still required today.

Rumor 1: “Any truck can now operate in Califo
ia” (False)

It is true that in 2025 certain Califo
ia Air Resources Board (CARB) regulations, such as Advanced Clean Trucks and Low-NOx Omnibus, were overtu
ed. These rules mainly affected manufacturers of new trucks.

However, the rules that determine which trucks are allowed to operate in Califo
ia have not changed.

The regulation known as the Truck and Bus Regulation is still in effect and requires that any truck operating in the state:

• Be registered with CARB

• Have a 2010 or newer engine model

• Pass emissions compliance requirements

If your truck could not legally operate in Califo
ia before, it still cannot operate there now.

Rumor 2: “Trump eliminated DEF” (False)

Although the Environmental Protection Agency (EPA) announced changes related to the 2009 endangerment finding, DEF systems remain mandatory under federal law.

What did change is how software-related issues are handled:

• The EPA issued guidance (not mandatory) allowing manufacturers to adjust engine derate software.

• This helps prevent trucks from entering reduced power mode or shutting down abruptly due to minor DEF system faults.

• These guidelines apply to model year 2026 and older trucks.

The Owner-Operator Independent Drivers Association (OOIDA) supported these changes, viewing them as more realistic for daily trucking operations.

DEF has not disappeared, but drivers now have more flexibility to address issues without being immediately placed out of service.

Rumor 3: “It’s now legal to remove the DPF” (False and dangerous)

Although President Trump issued a pardon to a mechanic previously convicted for tampering with DPF systems, removing or altering a DPF remains a federal offense.

Key points to remember:

• A presidential pardon does not legalize the practice

• DPF tampering still violates federal and state laws

• In Califo
ia, it can result in:

o Heavy fines

o An Out-of-Service order

o Serious issues during CHP inspections and BIT audits

Proposed bills to decriminalize these practices have not been approved.

Removing a DPF is still illegal and can be extremely costly.

Recent policy changes have reduced pressure on manufacturers and eased some electronic system behaviors, but they have not eliminated legal obligations. In Califo
ia, CARB, DEF, and DPF requirements are still very much in force.

Keeping your emissions system in proper working order doesn’t just help you avoid fines—it protects your equipment, your business, and your right to stay on the road.