U.S. Steel and Nippon Steel filed lawsuits against the Biden administration after their $15 billion merger was blocked, claiming the decision was politically motivated and prejudiced. They assert their right to a fair review was violated, and argue that the merger would strengthen U.S. national security. Additionally, they accuse rival Cleveland-Cliffs and the United Steelworkers union president of engaging in anticompetitive practices to thwart the deal. Biden defended the block, citing concerns over national security and the need for a domestically controlled steel industry.