Tesla boss Elon Musk has accused US regulators of targeting him for "unrelenting investigation" because of his criticism of the government.
In a court filing, the billionaire says the Securities and Exchange Commission has engaged in "outsized efforts" to monitor the firm that "seem calculated to chill his exercise" of free speech.
The letter heightens the battle between Mr Musk and financial regulators over his social media activity.
His Twitter posts often move markets.
In 2018, the SEC ordered Mr Musk to submit to increased oversight of his posts about Tesla as part of a settlement into claims that he misled investors in 2018 with a post about taking the electric car company private.
The SEC has repeatedly raised questions since about Mr Musk running afoul of the agreement, in which Mr Musk agreed to give Tesla officials pre-approval of posts about the company.
