But if we are only allowed to leave Australia when the bio-security emergency ends then surely they can't enforce it under bio-security laws.
The Bio-security Act 2015 of some ~700 pages is in force at all times.
Amongst a heap of different sections in the act, It allows all sorts of measures and determinations to be put in place against individuals regardless of the current declared emergency associated with Covid.
44 Entry requirements
(1) This section applies for the purpose of preventing a listed human disease from entering, or establishing itself or spreading in, Australian territory or a part of Australian territory.
(2) The Health Minister may determine one or more requirements for individuals who are entering Australian territory at a landing place or port in accordance with Division 2 or 3 of Part 4 of Chapter 4.
Note: An individual who fails to comply with a requirement may contravene a civil penalty provision (see section 46).
(3) A determination made under subsection (2) is a legislative instrument, but section 42 (disallowance) of the
Legislation Act 2003 does not apply to the instrument.
Where requirements apply
(4) The determination must specify where the requirements apply.
Kinds of determinations that may be specified
(5) Without limiting subsection (2), the determination may specify:
(a) requirements for all individuals, or classes of individuals; and
(b) specific requirements in relation to specified listed human diseases; and
(c) general requirements in relation to listed human diseases generally; and
(d) requirements relating to the manner in which an individual must comply with a requirement.
(6) Without limiting subsection (2), the determination may specify one or more of the following requirements:
(a) a requirement for an individual to provide either:
(i) a declaration as to whether the individual has received a specified vaccination or other prophylaxis within a specified previous period; or
(ii) evidence that the individual has received a specified vaccination or other prophylaxis within a specified previous period;
(b) a requirement for an individual to complete a questionnaire on his or her health, which may include confirmation of whether the individual is undergoing or has undergone specified treatment within a specified previous period;
(c) a requirement for an individual to provide a declaration in relation to a specified listed human disease;
(d) a requirement for an individual to provide a declaration or evidence of where the individual has been before entering Australian territory;
(e) a requirement for an individual to be screened (whether by requiring the individual to be screened by equipment, by providing a declaration, or in any other way).
Note 1: An officer has certain powers in relation to an individual who fails to comply with a requirement in subsection (6) (see section 60 (imposing a human biosecurity control order on an individual)).
Note 2: A person may commit an offence or contravene a civil penalty provision if the person provides false or misleading information or documents (see sections 137.1 and 137.2 of the
Criminal Code and sections 532 and 533 of this Act).
Note 3: This section is not subject to the privilege against self‑incrimination (see section 635).
(7) A determination must not specify as a requirement a biosecurity measure described in Subdivision B of Division 3 of Part 3 (biosecurity measures that may be included in a human biosecurity control order).