The Supreme Court ruled unanimously Monday that the Bush administration can skip a lengthy environmental study and open U.S. roadways to Mexican trucks as soon as it wishes.

The high court ruled against labor and environmental organizations that have long battled expansion of Mexican trucking within the borders of the United States despite a guarantee this country made when it signed the North American Free Trade Agreement more than a decade ago.

The president has authority to open the border, the high court ruled, and a federal agency responsible for truck safety has no say in the matter. Thus, the agency was under no obligation to study environmental effects from opening the border, as a lower federal court had ordered.

“The Court’s decision,” commented Gail Ruderman Feuer, a senior attorney with the Natural Resources Defense Council, which intervened on the case, “will increase deadly particulate pollution and smog by allowing tens of thousands of dirty diesel trucks from Mexico to travel into communities in the U.S. already plagued by poor air quality.”

According to NRDC:

At least 30,000 Mexico-domiciled diesel trucks could enter the U.S. starting this summer, including many older, pre-1994 trucks that are the most egregious polluters.

A study shows that by the year 2010 trucks from Mexico will emit twice as much particulate matter and nitrogen oxides as U.S. trucks.

There is no system in place to inspect the emissions of trucks coming over the border from Mexico.

For many model years, including trucks currently for sale, U.S. emissions standards are dramatically more stringent than those governing the sale of trucks in Mexico.