The U.S. Securities and Exchange Commission is asking a court to intervene and compel Elon Musk’s testimony following his “blatant refusal to comply” with a subpoena related to its probe of the billionaire’s public disclosures leading up to his $44 billion purchase of Twitter last year.

The SEC, which for years has tussled with Musk over a range of issues, said in its filing Thursday in federal court for the Northern District of California that it feels it has been stonewalled by Musk since serving a subpoena in May requiring that he testify at the SEC’s San Francisco office on a date to be agreed on in September.