Tesla repeatedly violated labour laws, including with an anti-union tweet from company boss Elon Musk, a US authority has ruled.
The National Labor Relations Board (NLRB) said in a judgement published Thursday that the dismissal of an employee who had campaigned to form a union was illegal.
Tesla must compensate the man for any loss of income and offer to re-hire him, the NLRB decided.
In addition, the authority said Musk must delete a tweet from 2018. The NLRB said Musk illegally threatened employees with the loss of their stock options if they unionized.
There was no immediate comment from electric carmaker Tesla or from Musk. The firm has denied misconduct.