The United States continues to use a unique set of safety and emission regulations for motor vehicles, which differ significantly from the internationalised ECE Regulations used throughout the rest of the world. Vehicle manufacturers thus face considerable expense to type-certify a vehicle for U.S. sale, at a cost estimated to be upward of USD $2 million per vehicle model. This cost particularly impacts low-volume manufacturers and models, most notably the makers of high end sports cars. However, larger companies such as Alfa Romeo and Peugeot have also cited costs of 'Federalizing' their vehicle lineups as a disincentive to re-enter the U.S. market.

NHTSA and EPA regulations criminalise the possession of a vehicle not meeting U.S. standards. Even Canadian-market vehicles may not meet these requirements. Exceptions exist for foreign nationals touring the US in their own vehicle and for cars imported for show or display purposes.

Because of the unavailability of certain cars, demand for grey market vehicles arose in the late 1970s. Importing them into the US involved modifying or adding certain equipment, such as Headlamps, sidemarker lights, and a catalytic converter as required by the relevant regulations. NHTSA and EPA would review the paperwork and then approve possession of the vehicle. It was also possible for these agencies to reject the application and order the automobile destroyed or re-exported. The grey market provided an alternate method for Americans to acquire desirable vehicles, and still obtain certification. Tens of thousands of cars were imported this way each year during the 1980s.

The Lamborghini Countach was one of the first grey market vehicles, encouraging the Italian manufacturer to prepare a U.S. model. The Range Rover was initially available only through the grey market, and the popularity of the model eventually convinced the parent company to re-enter the U.S. market in 1987. Other manufacturers, like PSA Peugeot Citroën with the CX and Renault with the mid-engine Renault 5 Turbo, missed the signals sent by the grey market about American consumer tastes and demand.

This avenue was increasingly successful, especially in cases where only lower-specification models were officially offered on the US market. For example, Mercedes-Benz chose to offer only the lower-output 380SEL model to Americans in 1981, ensuring a huge demand for the much faster 500SEL available in the rest of the world. BMW had the same issue with their 745i Turbo. The grey market was successful enough that it ate significantly into the business of Mercedes-Benz of North America and their dealers. The corporation launched a successful million-dollar congressional lobbying effort to stop private importation of vehicles not officially intended for the U.S. market. An organisation called AICA (Automotive Importers Compliance Association) was formed by importers in California, Florida, New York, Texas, and elsewhere to counter some of these actions by Mercedes lobbyists, but the Motor Vehicle Safety Compliance Act was passed in 1988, effectively ending private import of grey-market vehicles to the United States. No evidence was presented that grey-import vehicles' safety performance differed significantly from that of US models, and there have been allegations of improper lobbying, but the issue has never been raised in court.

It is no longer possible to import a non-US vehicle into the United States as a personal import, with some exceptions. For example, an individual can import a vehicle manufactured to Canadian motor vehicle safety standards if the original manufacturer issues a letter stating that the vehicle also conforms to US motor vehicle standards. The decision to issue a compliance letter is solely at the discretion of the manufacturer, even if the vehicle is known to meet US standards. Before issuing a compliance letter, most manufacturers request proof that the owner of the vehicle is a resident of Canada, and that the car was registered and used in Canada for a minimum period. This is done because the manufacturers maintain separate pricing structures for the US and Canadian markets.

In 1998, NHTSA granted vehicles over 25 years of age dispensation from the rules it administers, since these are presumed to be collector vehicles.[2] It is also possible to certify the car though a Registered Importer for DOT work and an Independent Commercial Importer for EPA work.[3] Those who import nonconforming motor vehicles sometimes bring in more than one car at a time to spread the cost of the necessary destructive testing, modification, and safety certification. Destructive crash testing is not always needed if the vehicle can be shown to be substantially similar to a model sold in the US. The Smart Fortwo is imported in this manner. Finally, the Show or Display law allows temporary import of noncompliant vehicles for show or display purposes.

One vehicle with grey market-related notoriety is the Nissan Skyline. In 1999, a California company called Motorex had a number of R33 GTS25s crash-tested. They submitted their information to NHTSA and petitioned for 1990-1999 GT-Rs and GTSs to be declared eligible for import.[4] Many Skylines were subsequently imported through Motorex. This lasted until late 2005, when NHTSA learned not all 1990 through 1999 Skyline models would perform identically in crash testing. Motorex had submitted information for only the R33, but had asserted that the data applied to R32, R33, and R34 models.[4] NHTSA determined that only 1996-1998 R33 models have been demonstrated as capable of being modified to meet the federal motor vehicle safety standards, and that only those models are eligible for import. In March 2006, Motorex ceased all imports and Motorex principal Hiroaki "Hiro" Nanahoshi was arrested and held on $1 million bail on financial, kidnapping, and assault charges

It's really not even the whole RHD allure that interests me in the car to be honest... The prices just seem to be cheaper... If I wanted to be JDM Tyteee I would just do the RHD conversion, but why? Added cost, more work than it's worth and then you can't hit mcdonalds on a cruise unless you get out of the car and go in... or have some awesome reverse skills...

LEGAL... 100% LEGAL was my question, I have never been a fan of bucking the system because in all honesty, it WILL bite you sooner or later... it happened to my buddy Mike back in FL... had a beautiful 800+ AWHP R32 GTR that had a Nur Spec R34 RB26 swapped into it as the base engine by him... One day he had a guy show up with a flat bed and a seizure notice and there was absolutely not one thing he could do about it... 50k + in that car and all he has to remember it by is pictures now... That is what I want to avoid... if it's able to be done legally (for a reasonable cost) then sure, it might be worth it, but if it is going to cost me more than 10k total (the median cost of a 100k mile FD) then what is the true point? to be cool? no thanks...