A Washington state home-care company unlawfully disciplined four of its employees during a unionization push and must now bargain with the union, the D.C. Circuit said April 30.

The four workers also must be reinstated to their positions with backpay, according to the court’s per curiam order. The National Labor Relation Board’s ruling that Kitsap Tenant Support Services Inc. bargained in bad faith after its workers voted to unionize was also affirmed by the appeals court.

Federal law protects...