Greenlight's letter came one day after Musk, a longtime critic of short-sellers, appeared to taunt the U.S. Securities and Exchange Commission by calling it the "Shortseller Enrichment Commission" on Twitter.
But some former SEC officials and legal experts were divided over whether Musk's comment had crossed a legal line.
"Just want to that the Shortseller Enrichment Commission is doing incredible work".
Mr Musk, 47, has long had a hatred of shortsellers - investors who have been betting on a fall in Tesla stocks. Here he's suggesting that the agency-whose mission is to protect investors from CEO misconduct-is actually harming the value of Tesla's stock by enforcing securities laws against Musk and Tesla.
The SEC believed the tweet caused significant market disruption, and went on to charge Musk of fraud and tried to bar him from taking an executive role at any public company. The SEC also alleged that Musk rounded up the buyout price for Tesla to US$420 a share to amuse his girlfriend at the time with a marijuana-culture reference.
But two days after the settlement, Musk had already raised eyebrows by tweeting out the video for "OPP", a 1990s hip-hop tune by the group "Naughty by Nature", along with a winking emoji, at 1.22am California time.
Musk was subsequently forced to give up his position as Tesla chairman and pay a $20-million penalty to settle fraud charges. He then wrote "what they do should be illegal". Tesla didn't immediately respond to requests for comment.
The website description says they want to help Musk with this "preposterous" SEC filing against him.
She has asked Tesla and the SEC to send a joint letter to explain why the settlement is "appropriate" before she reviews the case.
Judge Alison Nathan said the court needs to see justification that the settlement is "fair and reasonable".
Back in May, Musk rudely cut off analysts on Tesla's first-quarter earnings call.