The SEC's allegation of fraud against Mr Musk related to tweets he posted in August in which he said he was considering taking electronic vehicle maker Tesla off the stock market and into private ownership.
Musk has long feuded with short sellers, a category of investors that have been betting on Tesla's stock to fall. Under the terms of the settlement, Musk doesn't admit or deny the allegations in the agency's lawsuit against him, but he will step down as the chairman of Tesla's board of directors for three years and pay a $20 million fine.More news: Minnesota Birds Are Getting 'Drunk' On Fermented Berries, Police Say
The share price climbed as much as 11pc and by the close of play, Tesla's value had jumped by $6.3bn (£4.9bn) and Mr Musk was $1.2bn richer. Ryan White, an SEC spokesman, declined to comment. The fact that he's mocking the SEC begs the bigger question of where his head's at.
Musk agreed to settle the agency's case against him on September 29.
The settlement mandated that the company must implement "mandatory procedures and controls to oversee all of Elon Musk's communications regarding the Company made in any format".More news: USA vice president says China interfering in American politics
The SEC said those claims were "false and misleading".
Elon Musk has criticized investment fund managers like BlackRock for supporting short sellers, a group of investors who have been on Musk's radar since his announcement to make Tesla private. But that doesn't mean Tesla's board can't order Musk to tone done his Twitter act in the best interests of the company.More news: Chelsea linked with a move to re-sign Declan Rice
Musk has kept up his cryptic ways this week, tweeting out a music video by rap group Naughty by Nature for their 1991 hit song "O.P.P". "Maybe a 420M fine would have been more appropriate?" one Twitter follower said.