Radar Detectors Are Legal in Colorado; Jammers Are a Crime

Colorado never legislated against the receive-only radar detector. The prohibition the General Assembly did enact, § 42-4-1415, was added in 2005 and is aimed at the opposite device. Subsection (1)(a) makes it unlawful to use, possess or sell a radar jamming device, and (1)(b) separately makes it unlawful to operate a motor vehicle with one in it. The definition at (2)(a) is what draws the line: a radar jamming device is any active or passive device, instrument, mechanism or equipment "designed or intended to interfere with, disrupt, or scramble the radar or laser that is used by law enforcement agencies and peace officers to measure the speed of motor vehicles", and the statute names jammers and scramblers as examples. A detector emits nothing at the police unit; it listens. The operative verbs in the definition, interfere, disrupt and scramble, are not satisfied by receiving a signal.

The negative is not an argument from silence. A word search of the full official text of title 42, Vehicles and Traffic, as published by the Office of Legislative Legal Services, returns zero occurrences of "detector" in the entire title, and § 42-4-1415 is the only section in title 42 that uses the word "radar" at all. In title 18, the Criminal Code, "detector" appears only in § 18-3-407.5, which concerns an electronic lie detector examination of a victim of a sexual assault. The Colorado prohibition stops at the jamming device.

Note that the definition expressly includes a "passive" device. That word does real work: a jammer that reflects or absorbs a laser pulse rather than transmitting a counter-signal is still caught, so long as it is designed or intended to interfere with, disrupt or scramble police speed measurement. Laser shifters and reflective coatings sold for defeating lidar sit inside § 42-4-1415, not outside it. The one carve-out is at (2)(b): a radar jamming device does not include equipment that is legal under FCC regulations, "such as a citizens' band radio, ham radio, or any other similar electronic equipment". That protects lawful transceivers in the cab, not a device sold to beat a speed reading.

Commercial vehicles are the exception to Colorado's permissive position on detectors, and the rule reaching them is a state one. Under C.R.S. § 42-4-235 (4)(a)(I) the chief of the Colorado State Patrol adopts rules for the operation of commercial vehicles using the current United States Department of Transportation safety regulations as guidelines. The resulting rule, 8 CCR 1507-1, states at MCS 6 that all intrastate and interstate motor carriers, commercial vehicles and drivers thereof operating within Colorado must operate consistently with the safety regulations detailed in a list of federal parts that includes 49 CFR 392, as revised October 1, 2025. Section 392.71(a) of that part provides that no driver shall use a radar detector in a commercial motor vehicle, or operate a commercial motor vehicle that is equipped with or contains any radar detector, and (b) forbids a motor carrier to require or permit a driver to violate that. Because the Patrol rule reaches intrastate carriers as well as interstate ones, a Colorado-only truck is covered.

Mounting is the remaining constraint on an otherwise lawful device. Section 42-4-201 (4) requires that the driver's vision through any required glass equipment be normal and unobstructed, and there is no Colorado list of permitted windshield attachments to fall back on. A detector suction-cupped low on the windshield in the sweep of the driver's forward view is therefore the exposure, not the detector itself. Colorado runs no periodic safety inspection, so nothing is checked on a schedule; the encounter that matters is the roadside stop authorized by § 42-4-203 (1), under which a uniformed police officer may on reasonable cause require a driver to stop and submit the vehicle and its equipment to inspection.

Using, possessing or selling a radar jamming device, or driving with one in the vehicle, is a class 2 misdemeanor traffic offense under § 42-4-1415 (4), punishable as provided in § 42-4-1701 (3)(a)(II)(A). That schedule sets a minimum sentence of ten days imprisonment or a $150 fine or both, and a maximum of ninety days imprisonment or a $300 fine or both. This is a criminal charge, not the civil traffic infraction that governs nearly every other equipment rule in article 4 of title 42.

Subsection (3) adds a property consequence: radar jamming devices are subject to seizure by any peace officer and may be confiscated and destroyed by order of the court in which the violation is charged. Subsection (5) exempts peace officers acting in their official capacity. None of this attaches to a radar detector in a private vehicle. For a commercial driver, a detector violation is enforced through the Colorado State Patrol under 8 CCR 1507-1 and exposes the carrier to the civil penalties authorized by 49 CFR 386 subpart G, which § 42-4-235 (2)(a) makes applicable to intrastate carriers as well.