To add a bit, obviously this was outside of Germany's borders and direct jurisdiction. Does that mean a German citizen can use German public money to perform actions that are against the convention on human rights abroad? And, similar to how the getaway vehicle provider gets a different sentence than the mastermind who also held the gun, probably there is reduced responsibility here. But is there none at all?

And all this is still besides the question whether the employment was necessary and the least-invasive method possible. If you can prove a need greater than the lost privacy, as well as the lack of an alternative option, if I understand how the system works correctly, then it's perfectly legal also inside of Germany.