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."

The ruling was a potentially vast expansion of corporate legal liability, especially for companies that franchise their brands. The Hy-Brand ruling returned the standard to direct control, a decision cheered by business groups and slammed by labor unions and their allies.

In the letter, the Democrats strongly implied that Emanuel's deciding vote in the case is tainted because his former law firm, Littler Mendelson, represented one of the parties in Browning-Ferris Industries.

"Given that your former partners at Littler Mendelson P.C. represented a party in [the Browning-Ferris case] before the board, did you recuse yourself from the board’s decision to move to remand the [Browning] case from the U.S. Court of Appeals for the D.C. Circuit back to the board? If not, why not?" the lawmakers asked. They also asked if Emanuel would recuse himself should the case be sent back to the board.

The lawmakers do not charge that Littler Mendelson was directly connected in the Hy-Brand case but do request that Emanuel provide "any communications" between him and the firm relating to the case.

The letter was dated Dec. 21 and signed by Sens. Patty Murray of Washington, Maggie Hassan of New Hampshire, and Elizabeth Warren of Massachusetts, and Rep. Bobby Scott of Virginia, Donald Norcross of New Jersey, and Gregorio Sablan, the delegate from the Northern Mariana Islands.

Emanuel, a President Trump appointee who was confirmed by the Senate in September, responded to an earlier inquiry by Warren regarding his work with Littler Mendelson by saying he would recuse himself from any case involving clients of his former employer “for two years following my appointment to the NLRB.” He provided a list of hundreds of those companies, which included such names as Amazon, Carmax, DirecTV, FedEx Freight, Hearst Corp., JP Morgan Chase, M&T Bank, Nissan North America, Rite Aid, Staples, Target, Time, and Uber, among many others.

A representative for the NLRB could not be reached for comment.