South Dakota Radar Detectors: No Ban in a Car, a Class 2 Misdemeanor in a Truck Over 26,000 Pounds

South Dakota is one of the states that simply never legislated on radar detectors for ordinary drivers. That is provable rather than assumed. A full-text sweep of every chapter of SDCL Title 32, Motor Vehicles, returns no instance of radar, detector or laser. The nearest the Legislature came to regulating what a driver may receive inside the cab is SDCL 32-15-9, which makes it a petty offense to drive a motor vehicle equipped with any television viewer, screen, or other means of visually receiving a television broadcast located so that it is visible to the driver. That section was written in 1951 and reaches a television broadcast, not a police radar return, so it does not touch a detector.

The real restriction reaches commercial drivers, and it arrives by adoption rather than by a South Dakota-drafted prohibition. SDCL 49-28A-3 adopts the federal motor carrier safety regulations at 49 C.F.R. parts 390 to 397, as amended through January 1, 2026, and its first modification directs that all references to interstate operations must also include intrastate operations. Part 392 contains 49 C.F.R. 392.71, headed radar detectors; use and/or possession, which 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 that no motor carrier shall require or permit a driver to violate that rule. Possession in the cab is enough; the device does not have to be switched on.

The threshold in the South Dakota adoption is what a driver needs to know. The same subdivision (1) of 49-28A-3 exempts intrastate vehicles and combinations whose gross vehicle weight rating, gross combination weight rating, gross vehicle weight or gross combination weight does not equal or exceed twenty six thousand one pounds, that are not used to transport hazardous materials requiring placarding under part 177, and that are not designed to transport more than fifteen passengers including the driver. Cross that line in any of the three ways and parts 390 to 397 apply to a purely in-state run, radar detector rule included. The currency of the adoption is refreshed every session, most recently by SL 2026, ch 184.

Police radios are a separate subject and South Dakota does regulate those, which is worth knowing because the two are often confused. SDCL 23-4-2 forbids a person convicted of a felony in this state or elsewhere within the past ten years from possessing frequency modulation receiving equipment capable of being adjusted or tuned to receive messages on frequencies assigned by the Federal Communications Commission to local or state law enforcement, and makes a violation a Class 2 misdemeanor. SDCL 23-4-7, added by SL 2015, ch 135, makes it a Class 1 misdemeanor to possess any device actively receiving law enforcement or emergency dispatch audio or emergency dispatch text while committing a felony. SDCL 23-4-4 exempts holders of a valid FCC amateur radio operator or station license from the whole chapter. None of those sections reaches a radar detector, which receives a K, Ka or laser emission rather than an FCC-assigned law enforcement voice frequency.

Mounting is the remaining constraint, and it is the same one that governs any windshield accessory. A detector suction-cupped to the glass is nontransparent material upon the front windshield under SDCL 32-15-5, a petty offense unless it does not obstruct the driver's clear view of the highway or any intersecting highway. A detector hung from the mirror is an object or gadget dangling between the driver's view and the windshield under SDCL 32-15-6, a petty offense enforceable only as a secondary enforcement. A visor clip avoids both.

One more South Dakota point cuts against the usual reason people buy detectors. SDCL 32-28-21 forbids the Department of Public Safety and the Division of Motor Vehicles from entering any interstate compact to share information used to impose or collect a civil fine resulting from a violation captured by a red light camera or speed camera, and SDCL 32-28-22 restricts sharing under existing compacts. South Dakota has deliberately walled itself off from automated speed enforcement, so the detector is answering a hand-held or vehicle-mounted radar, not a camera network.

For a private motorist there is no offense at all: no South Dakota statute makes owning, mounting or using a radar detector unlawful in a passenger vehicle, and no fine, forfeiture or licence consequence attaches. For a driver inside the scope of SDCL 49-28A-3, the exposure is real. That section provides that any violation of the motor carrier safety requirements governing the driving of motor vehicles and the parts and accessories necessary for safe operation, found in part 387 and parts 390 to 396, is a Class 2 misdemeanor, which SDCL 22-6-2 sets at up to thirty days in a county jail or a five hundred dollar fine, or both.

R. 71(b) forbids a carrier to require or permit the violation. Enforcement runs through the Division of Highway Patrol under SDCL 49-28A-2, and out-of-service decisions follow the CVSA North American Standard Out-of-Service Criteria adopted at ARSD 61:23:01:04 in its April 1, 2025 edition, effective August 6, 2025. Separately, a person with a felony conviction within the past ten years who possesses a police-frequency FM receiver commits a Class 2 misdemeanor under SDCL 23-4-2, and possessing a device actively receiving dispatch audio while committing a felony is a Class 1 misdemeanor under SDCL 23-4-7, carrying up to one year in county jail or a two thousand dollar fine.