The post-11 September wiretapping law in the US has always come with a particularly frustrating catch for civil libertarians: Because the government wiretaps people in secret, no one knows for sure if they’re under surveillance, and so no one has proof of harm to challenge the law in court. That could change now thanks to an appeals court ruling this week, reinstating a lawsuit brought on behalf of more than a dozen media and civil rights groups, including Human Rights Watch, the PEN American Center and the magazine The Nation.

The American Civil Liberties Union filed the lawsuit challenging the Foreign Intelligence Surveillance Act, which allows the government to tap phone calls and read emails of Americans communicating internationally. The ACLU filed the suit on behalf of individuals and organisations “whose work requires them to engage in sensitive and sometimes privileged telephone and e-mail communications with colleagues, clients, journalistic sources, witnesses, experts, foreign government officials and victims of human rights abuses located outside the United States.” The latest appeal had also been supported by the Reporters Committee for the Freedom of the Press and numerous legal groups.

A district court dismissed the ACLU’s suit in 2009 on the grounds that the plaintiffs couldn’t prove they had been monitored under the law and so had no right to challenge it. This week, an appeals court reversed that decision, clearing the way for what the New York Times editorial board wrote could be “a significant — and far too long delayed— legal review of the statue.”