Solomon (left), who now works at the U.S. Department of Labor, served as the NLRB’s acting general counsel from June 2010 to November 2013. Obama nominated him to the general counsel post in January 2011, but the Senate returned the nomination. Obama renominated Solomon in May 2013, but he eventually withdrew it and nominated Richard Griffin Jr., whom the Senate confirmed.

The NLRB’s general counsel prosecutes unfair labor practices complaints. SW General Inc., a company that provides ambulance services to hospitals in Arizona, challenged an unfair labor practices complaint in part on the grounds that Solomon’s appointment was invalid at the time. The company, represented by Alison Davis of Littler Mendelson, argued that Solomon was ineligible to serve as acting general counsel once he became Obama’s nominee.

The D.C. Circuit panel agreed with SW General, finding that, under the Federal Vacancies Reform Act, an acting appointee can no longer serve once they become the nominee. There are exceptions to that rule, but they didn’t apply to Solomon, the court said.

The D.C. Circuit isn’t the first federal court to find fault with Solomon’s tenure. A federal district judge in Washington state ruled in August 2013 that Solomon’s appointment as acting general counsel was unlawful. The decision is on appeal before the Ninth Circuit.

Davis, who is the managing shareholder for Littler Mendelson’s D.C. office could not immediately be reached for comment. An NLRB spokeswoman said they were reviewing the decision. Solomon referred a request for comment for the Labor Department press office, which did not immediately respond to an inquiry.

Below: Read the decision in SW General v. National Labor Relations Board.