Turns out they're based in Switzerland, and have been around for a minute:

The Court of Arbitration for Sport (CAS; French: Tribunal arbitral du sport, TAS) is an international body established in 1984 to settle disputes related to sport through arbitration. Its headquarters are in Lausanne, Switzerland, and its courts are located in New York City, Sydney, and Lausanne. Temporary courts are established in current Olympic host cities.

https://en.wikipedia.org/wiki/Court_of_Arbitration_for_Sport