The purposes of this Act are:
(a) to provide for the protection by the Commonwealth of works and undertakings that are carried out for or in relation to:
(i) the defence of Australia ; or
(ii) the defence of Australia and the defence of another country; and
(b) to provide for the protection by the Commonwealth of areas that are reserved for:
(i) the defence of Australia ; or
(ii) the defence of Australia and the defence of another country; and
(c) to provide for the protection by the Commonwealth of works, undertakings and areas that require special security measures; and
(d) to provide for the protection by the Commonwealth of works, undertakings and areas in order to enable Australia to fulfil its obligations under treaties, conventions and international agreements relating to defence or security.