Updated April 2, 2014
The short answer is wait - enforcement of non-imported cars has been suspended.
Like many countries have done since the economic turn of the early century, Mexico has been closing loopholes in existing tax sources to raise more money for expanding social programs. In 2014 the rules and fees for importation of vehicles from north of the border were significantly changed, dramatically increasing fees, paperwork required and who would be allowed to act as agent.
Border residents that had made their living for decades as vehicle importers suddenly found themselves 'unqualified' and those that continued in the business found it reduced by 30% over the number of cars usually imported in that half of the year. The result was a number of border-crossing closing demonstrations by dealers and importers that shut down both Otay Mesa and San Ysidro. You can only imagine the chaos resulting.
This is an election year in Mexico and everything becomes a political football. The PRI wrestled control of the presidency from PAN of Fox and Calderon, and many feel that the PRI has reverted to its outdated conservative polices and protectionism. The importation law changes have been pointed out to benefit the wealthy in forcing purchase of new cars imported or locally manufactured cars, while denying access to used cars potentially protected under NAFTA and affecting the 85% of Mexicans who will never own a new car.
As the effects of a reduction of 30% in the availability of quality used cars the values of existing imported cars rose about 20%.
Where it stands now...
On March 16, 2015 Aduana stated there would be no adjustment to the new importation rules and fees and restrictions would remain as revised in 2014, despite protests. The requirement of a document stating country of origin would also be required. Since most North American car owners have no idea where the original of that document may have ended up, it required additional filing.
On March 18, 2015 the Used Car Dealers & Importers of the Border Region won an injunction against the current importation requirements.
Later the same day Aduana announced that enforcement of driving non-imported cars will be suspended through the end of 2015 or until the fee structure and requirements can be resolved.
On Monday, March 23, 2015 the PAN jumped right on this and pointed out that the protectionist policies of the PRI was affecting "the 85% of Mexicans that will never own a new car" and need to purchase quality import from north of the border. and how it was affecting a large number of car dealers and importers that had made their living from this business, reducing imports by 30% in a 6 month period. Remember, this is an election year.
The proposed new structure is amazingly similar to what had existed before, with a limit on how old a car may be and how young. Fees are determined on book value of the car, not what you may present a doctored receipt for what you bought it from your uncle for.
So, for right now cars may be imported, through the new system at inflated fees with special requirements, or you can wait., because they won't be enforcing driving an non imported car for the rest of 2015 or... now here is the tricky part... until the situation is resolved.
How this will play out will likely be in a way that give some leeway to cars already in the country, but know there is a good chance that sometime in the next year you will have to take a car back to the border for a couple of days to be imported, should the old system be returned.
Who must drive an imported vehicle?
AT THIS MOMENT April 2, 2015 – Nobody. The rules have been suspended. Even Mexicans can drive a non-imported car, for now.
What is likely to happen and who will need to import their vehicle
It is probable that the rules on importation will be returned to very close to what they were prior to 2014. The concession is likely to be enforcement to increase revenue. Local police can ticket and impound your vehicle once the tags are out of date, but they will not be able to establish your residency in relation to the importation of the vehicle. The state of issue of your driver license will have to match your plates and also be current.
However, if you are stopped by a federal highway officer, immigration officer, military or Aduana officer you can be required to show proof of visa, being tourist 180 day, Temporary or Permanent. You will be required to show proof of Mexican liability insurance to drive on Federal highways. Previous enforcement included Permanent Resident Visa holders in those that must drive imported vehicles.
This presents a problem for some "permanent" residents, as the visa no longer has a time limit on how long you can be out of the country. A legitimate permanent resident card holder could spend 6 months or more with the same car north of the border.
I am certainly not a mind reader of the Mexican congress, but if you are going to bring a vehicle into the country under this suspension I would anticipate that the rule affecting permanent residents to drive imported cars will fall in the favor of the tax man in the compromise.
For as long as I can remember I have been told that a person holding a Mexican driver's license can not drive a car with foreign plates. I would expect this to stand. There may be a grace period after the importation issue is resolved, but the suspension of enforcement will leave a big hole in government income, it will be resolved quickly I think.