Ketanji Brown Jackson, in her first published opinion as an appellate judge, sided with federal labor unions Tuesday in a dispute over when collective bargaining is triggered in the workplace.

Jackson, of the U.S. Court of Appeals for the D.C. Circuit, is reportedly a top candidate being considered to replace U.S. Supreme Court Justice Stephen Breyer, who announced his retirement last week. The 18-page opinion comes as she and her judicial writings will be under heightened scrutiny.