This is: ‘(a) invasion by foreign enemies to give laws and usurp the government, or (b) internal armed force in rebellion assuming the power of government by making laws and punishing for not obeying those laws. Usurped power involves organised tumult or open warfare, and must be something more than action by a mere unorganised rabble; it implies a more or less organised body with more or less authoritative leaders’. (F.H. Jones).