The Antarctic Treaty and related agreements, collectively called the Antarctic Treaty System or ATS, regulate international relations with respect to Antarctica, Earth's only continent without a native human population. For the purposes of the treaty system, Antarctica is defined as all of the land and ice shelves south of 60°S latitude. The treaty, entering into force in 1961 and currently having 50 signatory nations, sets aside Antarctica as a scientific preserve, establishes freedom of scientific investigation and bans military activity on that continent. The treaty was the first arms control agreement established during the Cold War. The Antarctic Treaty Secretariat headquarters have been located in Buenos Aires, Argentina, since September 2004.