Legal battles over Starbucks’ firing of union planners are heating up, as the U.S. Court of Appeals for the Sixth Circuit became the first federal appeals court to hear the company’s challenge to an order requiring the reinstatement of union supporters discharged last year.

During oral arguments Thursday, the coffee chain argued that an injunction sought by the National Labor Relations Board to maintain the workplace status quo should have been denied because there was insufficient evidence to show the firings eroded union support at the Memphis store. Starbucks said an election months later that resulted in the union winning certification was proof there wasn’t an atmosphere of fear clouding the bargaining process.