A federal appeals court in San Francisco has denied an emergency request to block Mexican trucks from gaining further entry into the United States.

A coalition of groups, including the Teamsters Union, The California Trucking Association and Public Citizen, among others, sought an injunction on Wednesday, two days before regulations over Mexican trucks were set to go into effect.
The 9th U.S. Circuit Court of Appeals turned down the request, which claimed trucks from Mexico will dramatically increase U.S. air pollution. Those filing the suit said at least 30,000 Mexico-domiciled diesel trucks are set to enter the U.S. this year, including many older, pre-1994 trucks they say pollute more than most U.S. trucks.
They claimed that the federal government did not conduct a thorough analysis as to the effects of this added pollution on the health of U.S. residents.
The ruling is expected to clear the way for Mexican trucks to gain complete access to the United States this summer, as called for in the long-delayed North American Free Trade Agreement. Currently they are limited to a narrow strip along the U.S. border with Mexico.