On January 1, 2019, a new law went into effect requiring all cars traveling on federal roads to have civil liability insurance. Civil liability insurance is third party liability insurance and covers damages to third parties and property. This is much like the temporary auto insurance you must have as a foreigner traveling into Mexico.
While the law was approved back in April of 2013, it was not put into enforcement on all vehicles until this year, and violators face fines ranging from 2,000-4,100 pesos. (about $100-$215 USD) When this law was first passed, it only applied to newer cars and certain values but as time went on, it applied to older models and now all cars.
The obvious goal here is to help protect victims of traffic accidents, which on average leave 44 dead and 369 injured every day. Vehicle accidents are the second cause of death in Mexico.
The minimum required limits for civil liability insurance is 100,000 pesos (about $5,200 USD) for persons and 50,000 pesos (about $2,600 USD) for property damage. Federal police have already started random checks on federal roads to ensure people carry the required insurance.