The high court backed the EPA's carbon emission cuts for large facilities, but said it has no rights over smaller polluters such as apartment buildings, schools or restaurants.
Total coal exports, however, fell 13.1% in the quarter, from 17.4 million tons in the first quarter of 2013 to 15.1 million tonnes in the same period this year.
A free fall in U.S. coal mining employment that began after a near-term peak in the final quarter of 2011 has extended into 2014, with first-quarter employment dropping by more than 5,700 jobs, or a decline of about 7.0%, compared to same quarter a year ago.