An American judge has ruled that Tesla broke "a series" of labour law.
The ruling states that the electric carmaker impeded with legitimate union organizing.
It also found that the firm must read a notice to workers explaining their rights in a meeting which has to be attended by Chief Executive Elon Musk.
The violations also included a tweet sent by Musk last year in which he says "Nothing stopping Tesla team at our car plant from voting union. Could do so tmrw if they wanted. But why pay union dues & give up stock options for nothing."