Is a catless downpipe legal for US street driving?
Fupower manufactures exhaust components including downpipes in T304 stainless with TIG-welded flanges, and the direct answer is no. A catless downpipe is not legal for street use in any US state, and nothing that changed in 2026 changed that.
Why, in one sentence. The prohibition is federal, not state. Removing or defeating a catalytic converter on a vehicle used on public roads is tampering under the Clean Air Act, and it follows the vehicle for its life rather than applying only when you are stopped.
What actually changed, and what did not. Three things happened in 2026, and all three are commonly misread. A June 29 presidential memorandum ("Freedom to Fix") directed EPA to clarify tampering enforcement policy, expedite aftermarket parts testing, and consider deprioritizing civil enforcement against individuals repairing back to stock configuration. On July 1, EPA recognized SEMA as an alternative certification authority, making SEMA's Certified-Emissions (SC-E) program a documented "reasonable basis" under EPA's Tampering Policy. And in January 2026, DOJ instructed federal prosecutors to drop criminal tampering charges under the Clean Air Act. What none of this did is create a legal street path for deleting a converter. EPA's own letters do not supersede the November 2020 Tampering Policy, and the July 1 guidance did not state that tampering enforcement against individuals would be deprioritized. SC-E also does not reach California, which still requires a CARB Executive Order for installed aftermarket parts. Most importantly, SC-E certifies that a part does not adversely affect emissions. A catless downpipe removes the converter, so it cannot earn that certification by definition.
The trap most owners miss. The 2020 Tampering Policy lists six forms of "reasonable basis" — restoring the original configuration, relying on a manufacturer's representation of identical performance, emissions testing, engineering expectation of lower emissions, EPA's voluntary certification program, and California certification. It then explicitly carves out on-board diagnostics: conduct affecting an OBD system may be enforced regardless of its effect on emissions. A catless downpipe almost always requires disabling or delaying the rear oxygen sensor monitor to keep the light off, which removes the defense rather than relying on it. Fitting the part and suppressing the code compounds the exposure instead of reducing it.
The "off-road use only" label is not a compliance path. SEMA's own guidance is blunt about this: "off-road use only" does not mean off limits from emissions standards, and in most cases those parts found their way to on-road applications, which is not Clean Air Act compliant. "Race use only" can be a legitimate label, but only when the manufacturer or retailer genuinely tracks where the part goes. A label does not transfer the compliance obligation to the buyer.
What is legal. Keep the factory converter and fit a cat-back or axle-back system, which sits behind the converter and stays inspection-friendly. Where the converter itself must be replaced, use a part with a documented reasonable basis — an SC-E certified part in the 49 states outside California, or a CARB Executive Order part in California — and keep the factory part for refitting. Where the car is genuinely a competition vehicle, a race-only part can be sold under an honest race-only label, but it should not be represented as street-legal, and the buyer should understand it cannot be registered for road use with emissions equipment removed.
Fupower states the limits plainly. Fupower does not describe or market catless downpipes as street-legal, and does not claim that a tune, a spacer, or a code disabled in the calibration makes a catless part compliant. Compliance is a documented engineering position, not a feature of the part.
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