In Norway 10 years ago, Anders Behring Breivik detonated a bomb in central Oslo, killing 8 people, and after that murdered 69 young people on the island of Utøya. Some say that we didn’t learn anything from it (link to article in Swedish).
However, not many say anything about a possible reason why authorities were not watching Breivik better and why the police was so late to stop him: About 20 minutes into a BBC documentary from 1992, Oswald LeWinter says there was an amendment to the NATO protocol, including an agreement of the government not to prosecute right-wing activists.
Norway is a member of NATO.
LeWinter is on Wikipedia described as not a credible source, but especially in this case it should be worth looking into if a blind eye had been turned against right-wing extremists. That governments make secret agreements must also be questioned.