The National Labor Relations Board said a 2018 tweet by Elon Musk was an illegal threat to UAW workers. A federal agency was wrong to order that Tesla CEO Elon Musk delete a 2018 social media post that union leaders saw as a threat to employee stock options, a sharply divided federal appeals court has ruled.The case involved a post made on what was then known as Twitter during United Auto Workers organizing efforts at a Tesla facility in Fremont, California.