Immigration – false imprisonment

High Court casenotes

In the High Court decision of Commonwealth of Australia v AJL20 [2021] HCA 21 (23 June 2021), the High Court was required to determine whether the respondent’s detention was unlawful and whether he was entitled to damages for false imprisonment.

The respondent is a Syrian citizen who arrived in Australia in 2005 as the holder of a child visa. In 2014, the responsible Minister cancelled the respondent’s visa on character grounds. As a result, the respondent became a “non-citizen” and was detained under the Migration Act 1958 (Cth) (the Migration Act).

The purpose of the Migration Act is described in s4 to include, among other things, to provide for the removal from Australia of non-citizens whose presence in Australia is not permitted under the Migration Act. To this end, s189(1) of the Migration Act requires an officer of the Executive to detain unlawful non-citizens.

Section 14 of the Migration Act defines an “unlawful non-citizen” to be a non-citizen in the “migration zone” (that is, broadly Australia) and is not a “lawful non-citizen”. A “lawful non-citizen” is defined by s13 of the Migration Act to be a non-citizen in the migration zone who holds an effective visa.

Section 196(1) of the Migration Act relevantly provides that an unlawful non-citizen is to be kept in immigration detention until removed from Australia pursuant to s198 of the Migration Act. And s198 of the Migration Act relevantly provides that an officer must remove, “as soon as reasonably practicable”, an unlawful non-citizen from Australia if the non-citizen’s application for the grant of a visa has been finally determined and refused.

In this case, although his application had been been finally determined and refused, the respondent’s detention was prolonged by some 14 months while officers considered Australia’s non-refoulement obligations (the obligation not to return an asylum seeker to a country in which they would be in likely danger of persecution).


But, importantly, s197C(1) of the Migration Act provides that whether or not Australia has non-refoulement obligations in respect of an unlawful non-citizen is irrelevant to the operation of s198 of the Migration Act.

The respondent successfully argued at first instance, in the Federal Court, that his prolonged detention was unlawful. The primary judge found that the Commonwealth had failed to remove the respondent “as soon as reasonably practicable” as required by s198 of the Migration Act.

The primary judge went on to find that, as a result of this failure, the detention of the respondent was not for the purpose of his removal from Australia and was therefore unlawful.

The Commonwealth appealed. The appeal was removed to the High Court pursuant to s40 of the Judiciary Act 1903 (Cth) because the dispute necessarily involved the interpretation of the Constitution. By a narrow margin of 4 to 3, the High Court allowed the Commonwealth’s appeal.

The majority (Kiefer CJ, Gageler, Keane and Steward JJ), in a single set of reasons, held that the primary judge’s reasoning was flawed in two ways. The first way, the majority considered at [39] was that the primary judge was wrong to read down s196(1) of the Migration Act.

The primary judge approached the construction of s196(1) “in light of” Chapter III of the Constitution which provides for the separation of judicial power from the executive and legislative powers. In his Honour’s view, the immigration detention scheme contained in the Migration Act, could not be validly enacted, under s51(xix) of the Constitution (naturalisation and aliens power), unless the Executive performed its duty, s198 of the Migration Act, to remove as soon as reasonably practicable.


The majority observed at [42] that the primary judge’s approach “conflated questions of constitutional validity with questions of statutory interpretation, and questions concerning the purpose of the [Migration] Act with questions concerning the purpose of the officers of the Executive bound by it”.

The majority noted at [43] that: “If the statute, properly construed, can be seen to conform to constitutional limitations upon legislative competence without any need to read it down to save its validity, then it is valid in all its applications, and no further constitutional issue arises. The question then is whether the executive action in question was authorised by the statute”.

The majority held that the immigration detention scheme was valid, and did not stray into judicial power, because the detention period was not determined by the Executive. Instead, the majority observed at [44] “the authority and obligation of the Executive to detain unlawful citizens is hedged about by enforceable duties, such as that in s198(6), that give effect to legitimate non-punitive purposes. Upon performance of these duties, the detention is brought to an end”.

The second way in which the majority considered, at [67], that the primary judge’s reasoning was flawed was in leaping to the conclusion that the Executive’s failure to remove the respondent, as soon as practicably possible, meant that the Executive was detaining the respondent for a purpose other than that permitted by the Migration Act. The majority held that this leap was unjustified. And the majority held at [73] that the Executive’s failure to discharge their statutory duty simply affords a basis for orders requiring the Executive to do their duty.

The majority accordingly allowed the Commonwealth’s appeal. But Gordon and Gleeson JJ, in a joint judgment, and Edelson J, in his own separate judgment, argued that the Commonwealth’s appeal should be dismissed.

Gordon and Gleeson JJ defined at [81] the central issue in dispute as being “whether detention is lawful even though it continues beyond the time at which it should have come to an end”. And Gordon and Gleeson JJ considered at [84] that “it is not the event of removal, but a time by which removal must occur, that defines the lawfulness of detention”.


Their Honours argued at [87] that the power to detain an unlawful non-citizen could only be understood by reference to “two interlocking dimensions – power and duration”. And their Honours contended at [98] that once it is accepted that the Executive’s power to detain under the Migration Act has “temporal bookends”, detention beyond the “terminating bookend” is unlawful.

Edelman J comes to the same conclusion as Gordon and Gleeson JJ. His Honour muses at [108] that it would be very strange if the Migration Act were “an island of freedom” in which the Executive could act for any purpose in the exercise of its powers no matter how far that purpose departs from the express or implied terms of statutory authority.

And his Honour also observes at [114] that the Executive could have simply given the respondent a bridging visa while they considered the Australia’s non-refoulement obligations.

Dr Michelle Sharpe is a Victorian barrister practising in general commercial, real property, disciplinary and regulatory law, p: 03 9225 8722, email The full version of these judgments can be found at

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