Car modifications have become so integral to car culture that it's hard to go a day without seeing at least one car that's received modifications from the automotive aftermarket world. But just because modifications are popular, that doesn't mean all of them are legal. As the aftermarket industry has evolved through the years, certain modifications began skirting state and federal laws of the U.S.

As such, measures have been taken to curtail a lot of these illegal car mods. Various localities have their own laws regarding modifications, but many modifications are illegal in the entire United States. So, before you decide to install a cold air intake or strap lightbars onto your car, consider first which modifications are legal and which ones are illegal in your neck of the woods.

Check out this list of the most popular modifications made to cars that are either illegal or, at the very least, frowned upon.

UPDATE: 2024/03/03 at 21:00

Are car mods illegal? It is hard to imagine that some of them are not legal in your area. With that in mind, we have refreshed and updated this list of illegal car mods, but it is up to you to check your specific area before making any changes to your ride.

In order to provide the most accurate information possible, we've relied upon data from manufacturer websites and other authoritative sources including MotorTrend, Car and Driver, and the EPA.

14 Overly-Bright Headlights Are Illegal

You would think having a car with extra powerful lights is a good thing on the road. While that might be the case for you, bright headlights, spotlights, and light bars are outlawed in many states because of the dangers they pose, not to you but to other motorists. Lightbars, in particular, are known for being extremely bright and powerful.

That's good news for you if you're off-road or in dark areas without traffic, but if you're going to use light bars on populated roads and highways, you're inviting danger for others and trouble from law enforcement authorities. Headlights must be between 500 and 3000 lumens as per the federal code of regulations.

13 Automatic License Plate Covers Are Against The Law

There's a cool factor that comes with automatic license plate covers, or at least those that we see in movies. No one will use automated license plate covers for giggles; people often use them with something heinous planned, and they install a license plate cover on their cars as a precaution for when things go awry.

Keep your license plates visible at all times folks. You could be in big trouble if caught with an automatic license plate cover on your car. States have varying laws on how covered your license plate can be, but it's illegal in every state to fully obscure it.

12 Rolling Coal Is Dirty And Illegal

If you've ever seen a pickup truck on the road that emits plumes of black smoke from its exhausts, there's a good chance that you're looking at a rolling coal truck. Those who turn their trucks into coal rollers even go so far as to modify their vehicles using smoke switches and smokestacks. While it is a spectacle in itself, the practice is also in violation of the Clean Air Act.

It prohibits the manufacturing, sale, and installation of a part for a motor vehicle that "bypasses, defeats, or renders inoperative any emission control device" and prohibits anyone from "tampering with an emission control device on a motor vehicle by removing it or making it inoperable prior to or after the sale or delivery to the buyer". Some coal rollers go even further, harassing other motorists with their smoke, and creating dangerous scenes on the road. Don't be that guy, folks.

11 Window Tints Aren't Illegal But Really Dark Ones Are

Car window tints are technically not illegal. Several manufacturers design high-quality window tints; you can buy them where they're available without getting into trouble. That means that darker window tints allow less light to enter the car. While that may be good in preventing your car's interior from turning into an oven, dark tint can also prevent people on the outside from seeing who or what is inside the vehicle.

If you have a car with a dark window tint, there's a good chance that someone from law enforcement will talk to you about it, depending on the laws within their jurisdiction. Michigan is the only state that allows any amount of tint on front windows. Conversely, New Hampshire, Vermont, and New Jersey allow no front window tint at all. All other states allow front window tints, some states as low as 20 percent maximum tint and others up to 70 percent. Back windows are less of an issue, though New York, Pennsylvania, and Rhode Island cap back window tint at 70 percent.

10 Red And Blue Lights Are Against The Law

Lights are probably the most popular modification done on a car. We already mentioned lightbars as being illegal on populated roads and highways, but at least lightbars can still be used in less populated areas and the world of off-roading.

Unfortunately, red, white, and blue lights — or police car lights, as they're more commonly known — are illegal. Expect a heavy fine if you get caught using police lights on your unmarked car, and be able to spend some time in jail too, because you'll likely be up there if you're caught using these lights.

9 Don't Jam My Laser

While laser jammers are technically legal to buy in the U.S., many states do not allow their use on the road. Jammers overwhelm the laser beam coming from laser guns so that the latter registers an inaccurate speed measurement or, in some cases, no measurement at all.

Laser jammers have been successful in that regard, and states have responded in kind by outlawing their use on the road. California, Colorado, Illinois, Iowa, Minnesota, Nebraska, Oklahoma, South Carolina, Tennessee, Texas, Utah, Virginia, and Washington D.C. ban the use of laser jammers.

8 Loud Muffler Systems May Sound Cool But Will Get You A Ticket

It's a common occurrence among car aficionados to have loud exhaust systems. Loud means proud, right? That's especially true when we're talking about high-powered sports cars with raspy V-8 engines sitting on idle, ready to wake up and let the entire neighborhood know about it. But just because it's legal, doesn't mean they should be without limits too.

All states in the U.S. have either banned or set rules in place to mitigate the use of obnoxiously loud exhaust systems. Washington, Oregon, California, Nevada, Montana, Michigan, Tennesee, Pennsylvania, Maine, and Connecticut use an objective method to determine whether the exhaust noise is too loud, while the others simply leave it up to the officer to declare it makes "excessive and unusual noise".

7 Cold Air Intakes Straddle The Thin Line Between Legal And Illegal

Cold air intake systems are one of the most important aftermarket upgrades you can give your car. Installing one in your ride usually nets more horsepower coming out of the engine, and more power means more fun, right? Having said that, is cold air intake legal?

Well, tell that to state regulatory authorities, many of whom have made cold air intake systems illegal within their respective jurisdictions. On the bright side, there are ways to legalize cold air intake systems across all 50 states. A specific unit must receive a CARB Executive Order (EO) number, which manufacturers of this aftermarket equipment must provide for each unit they sell.

6 Metal-Studded Tires Aren't Everyday Tires And Can Be Illegal

Studded tires are another confusing piece of equipment that jumps the fence between legal and illegal, depending on the location and situation. In the case of these tires, they're legal in many places, specifically where the winter season could turn those areas into frozen wonderlands. Studded tires are great for winter, but when it's not snowing and the roads are clear, they can destroy tarmac and road surfaces.

Five states prohibit metal studs entirely; Michigan, Florida, Texas, Hawaii, Louisiana, and Mississippi. On the other hand, Wyoming, Kentucky, Colorado, New Mexico, and North Carolina allow metal studs at any time. For all the other states there are conditions, mostly seasonal, as to whether you can use metal studs on your tires. So, while in most of the U.S., you can buy and use studded tires during winter, better to take those tires out from spring to autumn unless you want to get on the wrong side of the law.

5 Under-body Neon Lights Are Distracting And Are Banned In Some States

Fast and Furious fans from across the globe absolutely love the under-body neon lights. If you are honest with yourself, even if you are not a huge fan of the movies, having your car all lit up underneath like a moving orb looks cool. Unfortunately, it is so cool that it is distracting to other drivers.

Plus, the added glow can cause issues with the eyes of drivers passing by, or following, to the point of causing accidents. Underglow is completely illegal in Connecticut, Illinois, Maine, Massachusetts, Michigan, Minnesota, Pennsylvania, Virginia, and Washington. Most other states that allow the lights have restrictions like not allowing them to flash or rotate.

4 Bass That You Feel In Your Bones Is Not Always Legal

At one time or another, everyone has had the pleasure of hearing a car stereo so loud that it can be felt in the bones. Every time the bass hits, it is something felt as well as heard. A cool stereo system and entertainment center can be the party piece of a car.

The problem is that it is also felt by the people a block away, which can make it illegal in your area. Each local area will have a noise ordinance that limits the 'loud' a stereo can put off, so check out the laws before cranking it up.

3 A Lifted Truck Is An Awesome Mud Truck But Not A Legal Street Truck

Off-road enthusiasts understand that a lifted truck is essential when taking on a water-filled mud bog. Big 44-inch tires can really help churn up the mud that will surely be hidden under the layer of liquid. When on the asphalt, though, it can be hard to see the cars next to you at a stoplight, making things a little unsafe, which is why some states have limitations on how high you can lift a truck or SUV, so check the laws before adding any height to your suspension.

However, Alabama, Alaska, Arkansas, Arizona (provided you have flaps and fenders), Kansas, Kentucky, Louisiana, Montana, Mississippi, New Mexico, North Carolina, Oklahoma, Oregon, South Carolina, Texas, and Wyoming have no restrictions for body or suspension lifts.

2 Catalytic Converter Removal Gives Horsepower As Well As Fines

Old-school muscle car owners understand how much adding a basic catalytic converter can reduce horsepower, so it only makes sense that removing it would be a good idea. Granted, it can give you some horsepower if you make some modifications.

However, if you ever go through an inspection station and they notice the change, you can be looking at up to $10,000 in fines and a car that is impounded. Federal laws prevent tampering or removing any emissions device. On the positive side of things, you will probably not have to serve any jail time if you pay your fines off.

1 Nitrous Is Only Legal On The Race Track

Nitrous can give you an advantage on the quarter-mile track. Use of NOS could mean a win rather than a loss. However, many people have nitrous (NOS) hooked up in the car they use on the streets as their daily drivers or a weekend racer, which is where things become illegal. NOS can actually be legal in some states, like in Texas, or Illionois where there are no regulations for a NOS system in a car.

Maryland specifically bans it off of tracks and requires you to identify your car with a decal that indicates it has a nitrous injection system. The caveat here is that all states ban the possession of large quantities of nitrous oxide outside medical use, and consider it an illegal drug. Therefore, possession for use in a car could be considered similarly illegal.

Regardless of baseline legality, NOS is extremely dangerous when combusted in an uncontrolled environment. If something terrible should happen and emergency responders should be called, the nitrous oxide makes a highly volatile and unpredictable situation for them, putting lives in danger unnecessarily. So, keep NOS out of your street cars and all times.