"The Shortseller Enrichment Commission is doing incredible work".
Musk recently settled for $20 million with the Securities & Exchange Commission over a tweet he sent out during the summer regarding making Tesla a privately-owned company.
Musk is believed to have experienced a change of heart after seeing Tesla's stock plunge the following morning.
The tweet came five days after Musk settled SEC charges that he misled investors in tweets on August 7, including that there was "funding secured" to take his Palo Alto, California-based company private at $420 per share.
Tesla also accepted a $20m fine, despite not being charged with fraud.
The New York Times also said Musk had threatened to resign, in a phone call with directors, if the board insisted that he and the company enter into a settlement with the Securities and Exchange Commission (SEC).
Peter Henning, a Wayne State law professor who was formerly an SEC attorney, said: "It certainly shows his pique at having to settle".
The SEC declined to comment.
Tesla shares dropped as much as 3.5 percent to $272 after the close of regular trading.
While Musk wanted to fight the SEC, he reportedly had a change of heart when Tesla's stock plummeted almost 14 percent after the lawsuit was announced.
Elon Musk has hit out at the USA financial regulator just days after they reached a deal on fraud charges against him.
The 2nd Circuit has jurisdiction over Nathan's court, and Pritchard said the Citigroup decision likely foreshadows approval of Musk's settlement.
Pritchard said before Musk's tweet that he saw no "serious chance" for a rejection of Musk's settlement, based on 2nd Circuit precedent.
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.