5 USC 5109 - Positions classified by statute

(a) The position held by an employee of the Department of Agriculture while he, under section 450d of title 7, is designated and vested with a delegated regulatory function or part thereof shall be classified in accordance with this chapter, but not lower than GS14.
(b) 
(1) The position held by a fully experienced and qualified railroad safety inspector of the Department of Transportation shall be classified in accordance with this chapter, but not lower than GS12.
(2) The position held by a railroad safety specialist of the Department shall be classified in accordance with this chapter, but not lower than GS13.