Mexico's imposition of tariffs in early March 2009 affected 89 U.S. import goods. They were imposed in response to a provision in an appropriation measure passed by the U.S. Congress ending a pilot program that had allowed Mexican trucks to carry their cargo into the United States under NAFTA. Reaction to the Mexican tariffs was swift. Sen. Byron Dorgan, D-N.D., a main author of the language repealing the pilot program and whose home state's sunflower seeds and uncooked pasta were among the 89 items targeted, called it an "outrage."

However, Mexico's actions fundamentally differ from retaliations of other countries, such as Ecuador's raising tariffs on more than 900 items or India's 5 percent duty on imported steel. Mexico's retaliatory tariffs came only after it waited many years for the United States, its largest trading partner, to comply with its contractual obligation to allow its trucks to traverse U.S. highways.

NAFTA, signed Dec. 17, 1992, clearly states that Mexican trucks would "be permitted to enter and depart the territory of the United States through different ports of entry" three years after the agreement was signed. On Dec. 18, 1995, Mexican trucks were supposed to have been free to drive into the four U.S. border states (and U.S. trucks were to have been free to drive through the border into Mexico). Rather than giving the green light for Mexican trucks, however, the U.S. secretary of transportation abruptly announced a delay in the implementation of this provision. Processing of licenses for Mexican drivers was subsequently frozen, pending, according to the Office of the U.S. Trade Representative, further negotiations with Mexico. Mexico responded by reciprocally delaying access to U.S. trucks entering its territory.

Mexico waited three years for this "delay" to be resolved before taking action and bringing the issue before NAFTA's dispute-settlement body in 1998. In February 2001, the NAFTA panel found in Mexico's favor, giving Mexico the right to retaliate. Despite having the right to respond, Mexico exercised great restraint. It took no action, preferring to consult and cooperate with the United States and to seek alternative avenues for resolution. Since the decision, Mexico has bent over backward to assuage U.S. concerns, agreeing to subject its trucks and drivers to safety measures and tests above and beyond those applied to U.S. truckers and trucks—or to those from the other NAFTA partner, Canada. This despite the fact that safety statistics and safety studies indicate that both Mexican trucks and truckers have relatively fewer safety violations than their U.S. counterparts. It is only now, more than eight years later, having been painted into a corner by language in the appropriations bill, that Mexico has finally retaliated.