U.S. labor law prohibits employers from firing workers who band together to advocate for better working conditions. When the NLRB finds that firings violated the law, it can order that workers be reinstated and given back pay. Musk, also the head of electric-car maker Tesla Inc, has been in the headlines over his $44 billion acquisition of Twitter and attempts to remake the social media company after he warned of a potential bankruptcy. Musk also has been on trial this week over a shareholder challenge to his $56 billion Tesla compensation package.