Query: What prevented Canada from fully having their own army at the start?
Context: Its roots, however, lie in colonial militia groups that served alongside garrisons of the French and British armies and navies; a structure that remained in place until the early 20th century. Thereafter, a distinctly Canadian army and navy was established, followed by an air force, that, because of the constitutional arrangements at the time, remained effectively under the control of the British government until Canada gained legislative independence from the United Kingdom in 1931, in part due to the distinguished achievement and sacrifice of the Canadian Corps in the First World War.