Decisions at a glance: Administrative law

8 July 2022

Thoms v Commonwealth of Australia [2022] HCA 20

AGS instructed S P Donaghue QC Solicitor-General of the Commonwealth, with S B Lloyd SC and C J Tran for the respondent.

In Thoms, the High Court unanimously determined that the detention of Brendan Craig Thoms between 28 September 2018 and 11 February 2020 was not unlawful. In 4 separate judgments, the High Court found that section 189(1) of the Migration Act 1958 (the Act) validly authorises and requires an officer to detain a person if that officer reasonably suspects that the person is an unlawful non-citizen even if that person is not an alien.


Mr Thoms is a New Zealand citizen whose visa was cancelled in September 2018 by the Minister under section 501(3A) of the Act. He was subsequently detained under s 189(1) of the Act, which requires the detention of unlawful non-citizens (non-citizens who do not hold a valid visa). Mr Thoms commenced proceedings against the Commonwealth in the High Court for false imprisonment, arguing that section 189(1) of the Act could not support his detention as he was an Aboriginal Australian and therefore not an ‘alien’ within the meaning of section 51(xix) of the Constitution.

On 11 February 2020, a High Court by majority determined that Aboriginal Australians who satisfy the tripartite test in Mabo v Queensland [No 2] (1992) 175 CLR 1 [70] cannot be aliens in the constitutional sense and are not within reach of the aliens power in section 51(xix) of the Constitution (Love v Commonwealth, Thoms v Commonwealth (2020) 270 CLR 152 (Love/Thoms)). The majority also held that Mr Thoms is an Aboriginal Australian and not an alien. Mr Thoms was released from immigration detention that day.

The rest of Mr Thoms’ matter was remitted to the Federal Court of Australia for determination. A question was ordered to be heard and determined separately regarding whether Mr Thoms’ detention was unlawful. The determination of that question was then removed back into the High Court. 

Mr Thoms argued that his detention was unlawful because s 189(1) of the Act could not validly authorise detention of an unlawful non-citizens who is not in fact an alien.

Decision of the High Court

The High Court rejected Mr Thoms’ argument that section 189(1) of the Act only permitted the detention of aliens. The Court found, consistently with its reasoning in Ruddock v Taylor (2005) 222 CLR 612, that s 189(1) of the Act validly authorises and requires detention of non-aliens if an officer reasonably suspects, on objective grounds, that the person is an unlawful non-citizen). Assessing the reasonableness of the officer’s suspicion entails considering what is known or capable of being known by that officer at the time the person was detained. Since the officers who detained Mr Thoms knew he was a New Zealand citizen without a valid Australian visa and detained Mr Thoms in the period before Love/Thoms was decided, their actions were supported by the Act. The officers did not know, nor could reasonably have known, that the High Court would later decide in Love/Thoms that Mr Thoms could not be an alien due to his status as an Aboriginal Australian.

The Court’s decision confirms the Court’s earlier decision in Ruddock v Taylor (2005) 222 CLR 612 including in its application, until 11 February 2020, to a ‘non-citizen, non-alien’ such as Mr Thoms.

Further details on the decision.

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