Louisiana Never Wrote a Radar Detector Law: Legal in a Car, Barred in a Commercial Truck by Federal Rule

Louisiana Revised Statutes Title 32 is organised so that vehicle equipment offences are created by Chapter 1 and by nothing else. R.S. 32:53(A)(1) makes it an offence to drive a vehicle that is in an unsafe condition, that lacks the lamps and other equipment required "in this Chapter", or that is "constructed or equipped in any manner in violation of this Chapter". Subsection B then closes the loop in the motorist's favour: nothing in the chapter is to be construed to prohibit the use of additional parts and accessories on any vehicle not inconsistent with the chapter's provisions. A radar detector is an additional accessory, and there is no chapter provision it can conflict with, because the Legislature has never written one.

That is a positive finding, not an inference from silence. A full-text search of the Revised Statutes returns no section containing both the words radar and detector, and the word radar by itself appears in three places only. R.S. 32:1(3) and the identical definition in R.S. 32:43(B) define an "automated speed enforcement device" as an unmanned or handheld camera or optical device installed to work with a traffic control signal or radar speed detection equipment. R.S. 32:266 creates the Louisiana Highway Safety Fund, into which fines collected by a local law enforcement body for exceeding an interstate speed limit by less than ten miles per hour are paid, and which may be spent solely on permanent radar speed displays on interstate highways appropriated to the Department of Transportation and Development. Searches for jammer and jamming return nothing at all, so Louisiana has also not legislated against devices that interfere with police speed equipment.

What Louisiana has legislated, and heavily, is the enforcement side of the same technology. R.S. 32:43 forbids local municipal and parish authorities from installing or using automated speed enforcement devices on interstate roadways within their limits and confines those devices to school zones lawfully posted under R.S. 32:47, with an exception for Department of Transportation and Development construction zones where workers are present that expressly does not extend to local authorities. Note that this section is not fully statewide: Subsection A(4) disapplies it to the governing authority of a municipality with a population between fifteen thousand and sixteen thousand inside a parish with a population between seventy thousand and ninety thousand, according to the latest federal decennial census. R.S. 32:47, as amended by Acts 2024, No. 103 effective May 21, 2024 and Acts 2025, No. 107, requires that such devices be operated by sworn or P.O.S.T.-certified personnel and strictly prohibits deputized agents, contractors and subcontractors from operating them for mail citations. It also requires forty-eight inch by forty-eight inch bright yellow signs, bottom edge at least seven feet off the ground, reading "Photo enforcement devices at use", posted between five hundred and one thousand feet ahead, plus painted two-foot yellow stripes reading "Entering School Zone" and "School Zone Ahead". Criminal fines and fees cannot be imposed from a mailed camera citation and non-payment cannot be reported to a credit bureau.

Commercial drivers are the exception to the permissive rule, and the prohibition is federal rather than Louisiana's. 49 CFR 392.71(a) provides that no driver shall use a radar detector in a commercial motor vehicle or operate a commercial motor vehicle equipped with or containing any radar detector, and paragraph (b) forbids a motor carrier from requiring or permitting a driver to do so. Louisiana has not duplicated that rule in its own code: the State Police commercial inspection rules at LAC 55:III.825 and 827 adopt only three named federal provisions, 49 CFR 390.15, 396.17 and 396.21, all of them about periodic inspection and record keeping. For the Louisiana inspection programme LAC 55:III.825.A treats a vehicle as commercial at a weight rating of 10,001 pounds or more in interstate commerce, 26,001 pounds or more in intrastate commerce, if it is designed to carry more than fifteen passengers including the driver, or if it carries placardable hazardous material.

The practical Louisiana constraint on a detector is therefore not possession but placement. R.S. 32:361.1(B) prohibits operating a vehicle with any object or material placed on or affixed to the front windshield or the front side windows so as to obstruct or reduce the driver's clear view, and the four exceptions in Subsection C reach only tint film, a transparent strip in the top five inches, an unattached adjustable sun visor and law enforcement vehicles. A suction-cup detector on the glass is an object affixed to the windshield; the same unit sitting on the dashboard or clipped to a vent is outside the prohibition.

There is no Louisiana offence of possessing or using a radar detector in a private vehicle, so there is no fine, no forfeiture and no confiscation power to describe. Louisiana officers do not have a state charge available for the device itself. S. S. S. 32:57. 71 rather than a Title 32 charge, and the carrier as well as the driver is exposed under paragraph (b). S. S. S. 32:43(C) has since January 1, 2015 barred local authorities from imposing or collecting any civil or criminal fine, fee or penalty from an image produced in violation of that section.