The North Atlantic Treaty Organization is an intergovernmental military alliance based on the North Atlantic Treaty which was signed on April 4, 1949.
To get more information about the release of the prisoners from the Fridge, Skye hacked the NSA satellites. To make sure his involvement would not get public, Agent Grant Ward killed Agent Eric Koenig and stopped the feed. When Skye returned and asked about Koenig's location, Ward told her that he was sending the info to NATO, the CIA and Interpol.
During the Attack on the HYDRA Research Base, the Avengers fought and defeated Baron von Strucker. Baron von Strucker and the surviving HYDRA soldiers were taken into NATO custody following this defeat. Ultron would later on break into the facility and murdered Strucker and write the word "Peace" on his cell walls in Strucker's own blood.