The Supreme Court put the brakes on New York City's greener taxi efforts.
Federal judges had blocked the city's fuel regulations, designed to make taxi companies purchase more fuel efficient vehicles.
The Supreme court refused to hear the city's appeal, according to CBS New York.
Federal judges had reasoned that only federal agencies, and not local officials, can regulate fuel economy and emission standards.
In May of 2007, Mayor Bloomberg unveiled a plan that would gradually replace the city's current fleet of taxis with hybrid vehicles by 2012.
"It will be the largest, cleanest fleet of taxis anywhere on the planet," Bloomberg said at the time. "And because taxis are so heavily used, the new standard will have the equivalent effect of removing 30,000 individually-owned gas-powered vehicles from our streets."
Bloomberg also said hybrid cars would save cab drivers $10,000 a year on gasoline and other expenses.
Now those plans seem like a distant pipe dream for the Bloomberg administration.