According to the Encyclopaedic Australian Legal Dictionary, administrative law is:
"The legal principles governing the relationship between the government and the governed. The exercise of power by decision makers, including the state (the Crown), ministers, departmental officers, tribunals, boards, and commissions must be based on legal authority. The source of that legal authority may be statute or the common law, which includes prerogative power."1
1Encyclopaedic Australian Legal Dictionary (online at 24 January 2019) 'administrative law'.