In its ongoing "war on terror," the United States, for years, has been carrying out so-called targeted killings of suspected terrorists with the help of unmanned drone aircraft. Information about possible targets is also passed on to the US intelligence services by their German counterparts, who have gleaned that information from asylum seekers.

Germany's Central Survey Office (HBW) regularly conducts background checks on asylum seekers. The agency, like the Federal Intelligence Service (BND), answers directly to the chancellor, and is particularly interested in information about suspected terrorists in the asylum seeker's country of origin.

Theoretically, as German media have pointed out, the transfer of this information could lead to the targeted killing of a person by the United States, making Germany an indirect participant in that action – and that could be a violation of international law, according to Robert Frau, an expert on the subject at Viadrina European University in Frankfurt (Oder).

"If Germany were to hand over data to the Americans, which were then used for illegal actions, then Germany would be abetting a breach of international law," said Frau.

Interpretations of international law

There is no consensus among law experts, however, whether or not drone attacks and targeted killings are a violation of international law, and as such, whether Germany, in passing on information, would be abetting a breach of the law.

This MQ-9 Reaper is one of the main drones used by the US for clandestine air operations

In armed conflicts, persons participating directly in combat operations are legitimate targets. "In such cases, a drone attack is no different than using a missile, or having soldiers fire their weapons," said Frau.

A targeted killing in that scenario would not be a violation of international law. Both the United States and Germany, for example, are involved in an armed conflict in Afghanistan. Therefore, if Germany passes information to the US on German citizens in Afghanistan and the US uses that information for a targeted killing, that is not a breach of international law, Frau explained.

The situation would be different in Somalia, however. "Germany is not involved in armed conflict there and outside of an armed conflict there are other rules. That means, as a matter of principle, such killings are not legal," Frau stressed.

No German collusion is known

Hans-Christian Ströbele admits that no German participation is known

It is next to impossible to prove whether or not Germany in the past ever provided information that led to a targeted killing. When asked, the German government points to the necessity of keeping sensitive information secret.

Even the highly critical Green politician, Hans-Christian Ströbele, who is a member of the Parliamentary Control Committee that oversees the intelligence services and has access to secret government files, has said that he has no knowledge of any such cases.

Ströbele did say, however, that there was also no way to totally exclude it either. Germany, he said, had no way of knowing what the US did with the information it received from Berlin.

Once data is passed on, one can assume the US intelligence services will use it as they see fit, agrees law expert Frau. Germany "cannot pass on data with the explicit request that they not be used for illegal acts," he said.