DOVER, Del. (AP)- A federal appeals court has rejected Delaware's effort to prohibit what the state has called "non-essential" idling of trains delivering crude oil to the Delaware City refinery.



Prompted by complaints from area residents about noise and air pollutions, lawmakers passed a bill in 2015 prohibiting non-essential idling of locomotives between 8 p.m. and 7 a.m. Former Gov. Jack Markell then signed the bill into law.



But the federal Surface Transportation Board voided the law last year, agreeing with Norfolk Southern Railroad Co. that it is pre-empted by federal laws governing rail transportation.



Delaware challenged the ruling, saying its law was narrowly tailored.



A Washington, D.C., appeals court rejected Delaware's appeal Friday, saying the state law is categorically pre-empted by federal law, and that the state cannot control the railroad's operations.