Democratic lawmakers are demanding to know why a Republican member of the National Labor Relations Board, the government’s top labor enforcement agency, didn’t recuse himself from a case that overturned a key Obama administration-era precedent.

In a letter to the board, the lawmakers asked why William Emanuel, one of the board’s five members, didn’t recuse himself from the case Hy-Brand Industrial Contractors, which, in a 3-2 vote, overturned the board’s ruling in the 2015 case Browning-Ferris Industries. The latter case led to the board’s controversial decision to expand the “joint employer” standard for when one business is legally responsible for workplace violations at another company from “direct control” to the much vaguer “indirect control.”