A prominent Saudi dissident who worked closely with Jamal Khashoggi said he will pursue further legal action against X after a US appeals court said that a 2014 security breach of the company – then known as Twitter – by agents of Saudi Arabia caused him injury.

Private identifying information about Omar Abdulaziz, who lives in Canada and has been an outspoken critic of Saudi crown prince Mohammed bin Salman, was obtained by the Saudi government after Riyadh recruited two Twitter employees to access information about dissidents – including those who used anonymous accounts to criticize the kingdom.

The breach, which occurred about a decade ago and compromised about 6,000 accounts, was discovered in 2018 and had devastating consequences for Abdulaziz, including the imprisonment of his family members in Saudi Arabia. Saudi agents also obtained Abdulaziz’s mobile phone number, which was used by the kingdom – Citizen Lab researchers later reported – to hack Abdulaziz using NSO Group spyware at a time when he was in close contact with Khashoggi. The journalist was killed months later.

Abdulaziz has faced an uphill fight against Twitter and now X, which is now owned by Elon Musk, the billionaire adviser to Donald Trump.

An appeals court this month sided with X when it said that Abdulaziz’s case, which alleges that the social media app was negligent when it failed to stop Saudi operatives from gaining access to his account, ought to be thrown out because it did not meet California’s two-year statute of limitations.

However, the court also rejected a lower court ruling that said Abdulaziz did not have standing in the case. Instead, it said Abdulaziz had been harmed by the company’s alleged handling of the matter. Given that new finding, he is expected to file for an en banc review of the case on Wednesday, in which a court may decide to review the lower court decision again. Twitter said at the time it had been a “victim” of its employees’ misconduct.

The case has brought back into focus the persistent threat against activists and other critics of authoritarian governments who have faced harassment, surveillance and threats of violence from abroad, even within countries such as the US and Canada, which were once considered relatively safe havens from the reach of countries like Saudi Arabia, Iran, the United Arab Emirates (UAE) and India.

The Guardian reported in 2020 that Abdulaziz had been warned by police in Canada that he was a “potential target” of Saudi Arabia and that he needed to take precautions to protect himself.

Ronald Deibert, the founder and director of the Citizen Lab at the University of Toronto’s Munk School, which investigates digital threats to civil society, said he was worried “that the gains that have been made around mitigating transnational repression and regulating the tools used to undertake it, such as mercenary spyware, are at risk of being rolled back under the Trump administration”.

“In fact, there are good reasons to be worried that those very same tools could be abused by the administration itself to go after migrants, refugees, asylum seekers that are being targeted for deportation, as well as the investigative journalists who cover those topics,” Deibert said.

The Biden administration in 2021 placed Israel’s NSO Group, which sells surveillance software that has been used by governments to target journalists and activists, on a blacklist because it said the propagation of the company’s spyware represented a threat to US national security.

NSO’s lobbyists have sought to reverse that classification, which is controlled by the commerce department. Trump announced on Tuesday that he would nominate Wall Street executive Howard Lutnick, a strong supporter of Israel, to lead the department.

The starkest example of a case of transnational repression targeting a dissident with ties to the US was the 2018 killing of Khashoggi, which occurred under the first Trump administration. The US treasury department issued some sanctions against individuals in the wake of the murder. Weeks after entering the White House, US president Joe Biden released an unclassified intelligence report that said Prince Mohammed had approved the brutal murder.

In a statement to the Guardian, Abdulaziz said: “I am determined to fight to the very end because this legal battle is not just about seeking justice for what happened to me; it is about holding companies accountable for their responsibility to their users. No one should suffer the consequences of a hack because a company failed to do its job.”

The Guardian did not receive a response to a request for comment from X.

After Musk, the largest investor in X is a company headed by the Saudi billionaire Prince Alwaleed bin Talal, who was himself imprisoned by the Saudi government in 2017 as part of a so-called anti-corruption purge.

He has not left Saudi or the UAE since then, but recently met with X chief executive Linda Yaccarino, in an encounter billed as a way to highlight “ongoing connections between X and Kingdom Holding”, his company, which is partly owned by the Saudi government.

Yaccarino also met with Dubai leader Sheikh Hamdan bin Mohammed bin Rashid Al Maktoum on the same trip to the Middle East. Agents of Sheikh Maktoum used NSO spyware to target the phone of his ex-wife and her legal team in the UK in 2021, according to the findings of a British court.