The Securities and Exchange Commission on Tuesday filed a lawsuit against Elon Musk, alleging the X owner misled shareholders about his Twitter stock purchases in 2022.

The suit alleges Musk violated federal securities laws, enabling him to purchase shares of Twitter at artificially low prices before his $44 billion takeover of the social media site. Musk has called the SEC “just another weaponized institution doing political dirty work.”

Musk started buying shares of Twitter, which he later renamed X, in early 2022. By mid-March, he’d acquired ownership of more than 5% of the company’s outstanding stock, according to the SEC filing. He was required to file a report with the SEC disclosing his purchases, but the lawsuit alleges he failed to do so in a “timely” manner, allowing him to underpay other investors by at least $150 million for shares they bought during that period.