SAN FRANCISCO — The sister of an imprisoned Saudi dissident filed suit against Twitter on Tuesday, arguing that it broke the law by letting employees reveal his identity to Saudi agents who then arrested him.

The novel case, filed under the federal Racketeer Influenced and Corrupt Organizations statute, cites repeated security failures that allowed the spies working for Twitter to send information about thousands of anonymous users to the Saudi regime while royal funds were invested in the company, becoming one of its largest shareholders.

The case was filed in the Northern District of California by U.S. citizen Areej al-Sadhan on her own behalf and that of her brother, Abdulrahman al-Sadhan, who is jailed in Saudi Arabia under a 20-year prison sentence for supporting terrorism and prejudicing public order.

Various Saudi officials and the kingdom itself are also named as defendants in the alleged scheme. They would typically qualify for sovereign immunity under U.S. law. But there is an exception for commercial ventures, which is typically invoked in contract disputes rather than investments.

“Each member of the Saudi Criminal Enterprise participated in a conspiracy to chill anti-authoritarian advocacy by, among other conduct, unlawfully obtaining personal identifying information of political dissidents to identify and target them and kidnapping, torturing, stalking, harassing, threatening, and killing other political dissidents,” the lawsuit says. “Twitter became a participant tool of transnational repression to silence voices of dissent beyond Saudi Arabia’s borders in the United States and abroad, all in an effort to monetize its commercial relationship with Defendant KSA.”

KSA refers to the kingdom of Saudi Arabia.

Suing on behalf of someone who can’t come to the United States is also unusual. Courts allow a “next friend” to sue when the beneficiary of the claim is incompetent, which in California means that they are unable to help their attorney. The suit suggests that Abdulrahman al-Sadhan is by that definition incompetent, because he is imprisoned with virtually no ability to communicate with outsiders.

Twitter did not respond to a request for comment. The Saudi Embassy in Washington had no immediate comment.

The case builds on the conviction last year of one of the Twitter insiders who took bribes from Saudi intelligence. Ahmad Abouammo, who ran Twitter’s media partnerships in the Middle East, took hundreds of thousands of dollars to pass on information about critics of the Saudi rulers. Two others who were indicted fled the country.

Twitter is in a position to protest that it did not approve of the spying and that the insiders went to some lengths to hide their activity.

But al-Sadhan attorney Jim Walden said that the company’s failures were so glaring that it could be found liable under the theory of “conscious avoidance of criminality.”

In 2015, the suit notes, the FBI warned Twitter that it had a problem with Saudi spying. But top officials including former chief executive Jack Dorsey met with Saudi leaders, and the kingdom increased its stake in the company that year. It is now the second largest investor, after Elon Musk.

The U.S. Federal Trade Commission has brought multiple actions against Twitter for security lapses, and its former head of security told Congress last year that other countries also had spies inside the company and that executives were still failing to limit and track what employees were doing.

At least two other suits have been brought against Twitter over its role in the Saudi spying. One by Omar Abdulaziz was dismissed when a judge found that he had not established that the alleged leak of his information in 2015 led directly to the country hacking his phone three years later, then imprisoning his family and friends.

Another, by exiled dissident Ali al-Ahmed, was thrown out mainly for being filed in New York instead of the right jurisdiction.