On June 13, 2013, the Fifth Circuit Court of Appeals issued an opinion upholding a 2010 Dallas city ordinance that allows taxi cabs powered by compressed natural gas ("CNG") to have priority over gasoline-powered taxi cabs in lines for passengers at Dallas’ Love Field airport.

The Association of Taxicab Owners, which represents gasoline-powered taxis in the Dallas/Fort Worth area, challenged the ordinance on the basis that it was preempted by the federal Clean Air Act, as it constituted a backdoor manner of regulating new vehicle emissions. A three judge panel of the Fifth Circuit upheld the ordinance, finding that it did not impose emissions controls either directly or through its indirect effects, as it did not create a mandatory standard compelling the conversion of taxi cabs to CNG and taxi cabs had alternative available methods to recover any losses derived from losing a place in line at Love Field.