Whistleblower Edward Snowden can be asked to give evidence in person by a German committee probing the NSA's spying activities, the country's Federal Court of Justice has ruled.

Germany's government has been told that it should make suitable arrangements for that to happen. It has been refusing to invite Snowden to give evidence personally since it would need to guarantee that he would not be handed over to the US—a promise the German authorities say would risk damaging the political relations between the two countries.

Instead, it has called for him to give evidence via a video link, or for German officials to interview him in Moscow, both of which Snowden turned down.

Following a formal complaint by the greens and left-wing politicians, Germany's Federal Court of Justice has ruled that the German government must provide the necessary guarantees that would allow Snowden to give evidence in person, or explain why it will not do so.

Snowden's lawyer, Wolfgang Kaleck, told the Süddeutsche Zeitung that the German government might refuse to provide guarantees, and officially admit that it regards cooperating with the US on intelligence matters in the future as more important than getting to the bottom of past surveillance. In that case, an appeal could be made to Germany's constitutional court, according to an article in Der Spiegel, which would decide whether the German government was allowed to make that trade-off.

The committee of inquiry is examining to what extent German citizens and politicians were spied on by the NSA and its so-called Five Eyes partners—notably GCHQ—and whether German politicians and intelligence agencies knew about this activity.

The committee was set up in the wake of Snowden's revelations, and amid claims that even the German Chancellor Angela Merkel had been under NSA surveillance. The US said that was not happening, but didn't deny it had happened in the past.