Military and law enforcement checkpoints are aimed are detecting narcotics and firearms traffic. They are located at various places throughout México. Most checkpoints will have a red flag marker and are operated by the military. The checkpoints have "spiked devices" to be used to deflate tires of vehicles attempting to evade the checkpoint. There is a military checkpoint near the studio where your vehicle may be searched for weapons & drugs. Legality of a search is never an issue in a Mexican court of law. If contraband is found in your car, your conviction for that offense is likely. These checkpoints serve primarily as a deterrent and most vehicles are allowed to pass without inspection. Being courteous will serve you well.