It imposed exchange controls on non-sterling area countries, barring them from freely converting British pounds into US dollars, but no such restriction was placed on sterling area countries. As a colony of the British Empire, Hong Kong was obliged to observe the sterling area regulations. Nevertheless, its unique geo-economic position afforded Hong Kong the ability to defy exchange controls by operating a dual system with the sterling area and a free exchange market principally with the US dollar, which was technically illegal from 1949 to 1967.