The U.S. District Court for the District of Columbia has denied the American Trucking Associations' request that a full panel reconsider a panel's previous decision that California could continue to enforce its Transport Refrigeration Unit regulation
, according to ATA's Truckline newsletter.

The rule, adopted in February 2004, requires that TRUs equipped with diesel engines seven years or older be replaced or retrofit with new engines. This applies only to TRUs operating in California. While the rules were scheduled to take effect in December 2004, the California Air Resources Board had to get a waiver from the Environmental Protection Agency to enforce them. The rules were effective Dec. 31, 2009.

In April of this year, the U.S. Court of Appeals for the District of Columbia Circuit denied the ATA's request to reconsider the waiver.

In the most recent litigation, ATA argued that the rule was a de facto national standard because many trucks pass through California and will be subject to the rule. The recent decision ends the litigation, however, unless it gets U.S. Supreme Court review, ATA says.