The high court refused Monday to hear an appeal by city officials who want to make cab companies buy more fuel efficient vehicles.
Federal judges had blocked the city's new taxicab fuel regulations.
City officials first wanted new taxicabs in 2008 to get at least 25 miles per gallon and 2009 taxicabs to achieve 30 miles a gallon.
They then tried to force taxicab companies to go to hybrid cars by making it more expensive for them to buy fuel.
But federal judges say it's up to federal agencies, not local officials, to regulate fuel economy and emissions standards.
The case is New York City v. Metropolitan Taxicab Board of Trade, 10-618.
