CASA have the power to detain an aircraft if they choose. They also can, with a warrant, enter premises and seize evidential material. That might be a part, a document (either written or stored on a computer), or even an aircraft, as "evidential material".
32ACA Search with consent for evidence in relation to civil aviation offences
Subject to section 32ACB, if an investigator has reasonable grounds for suspecting that there is on, or in, any premises a particular thing which may be evidential material, the investigator may:
(a) enter the premises; and
(b) search the premises for the thing
32AK Powers in relation to aircraft etc.
(1) An investigator may, for the purpose of performing the functions or exercising the powers of an investigator under this Part in relation to an aircraft, vessel or vehicle, require the person apparently in control of the aircraft, vessel or vehicle to do either or both of the following:
(a) to stop and detain the aircraft, vehicle or vessel for such reasonable period as the investigator specifies;
(b) to take all reasonable steps to ensure that the aircraft, vehicle or vessel, or a specified part of it, is left undisturbed for such reasonable period as the investigator specifies.
(2) A person must not fail to comply with a requirement under subsection (1).
Penalty: 30 penalty units.
(3) Subsection (2) does not apply if the person has a reasonable excuse.
Note: A defendant bears an evidential burden in relation to the matter in subsection (3) (see subsection 13.3(3) of the Criminal Code).
(4) An offence under subsection (2) is an offence of strict liability.
Note: For strict liability, see section 6.1 of the Criminal Code.
If an inspector needs to inspect an aircraft in the field, the inspector should, where possible, carry out the inspection without requiring the opening of panels, dismantling or jacking. If a further internal inspection is required, then the inspector should obtain the consent of the owner, maintenance engineer in charge, or pilot-in-command of the aircraft. The person providing the consent should remove and replace any access panels. The inspector should generally not do this.
The operative word here is "should" which is not "shall" or "must". I don't know what powers apply if the owner declines to assist.
With respect to the Police and Motor Vehicles, they have broad powers to search if they believe the vehicle has been used, is being used, or is likely to be used, in the commission of an Australian road law offence. The officer may form the "necessary belief" during or after an inspection or independently of an inspection. They have no power to search a person under this act but no doubt their would be another piece of legislation to provide for this. Note that they can come to that "necessary belief"
after the inspection i.e. they can go on a fishing expedition if they so choose.
There is no direction in the legislation as to whether the officer has to advise any reason to the driver or owner of the vehicle prior to the search.
From the South Australian Road Traffic Act 1961
40R—Power to search vehicle on road or certain official premises
(1) This section applies to a vehicle located at a place—
(a) on a road; or
(b) in or on premises occupied or owned by a public authority, whether or not the vehicle is unattended.
(2) An authorised officer or police officer may search a vehicle for compliance purposes, if the officer believes on reasonable grounds that—
(a) the vehicle has been used, is being used, or is likely to be used, in the commission of an Australian road law offence or in the commission of a breach of an approved road transport compliance scheme; or
(b) the vehicle has been or may have been involved in an accident.
(3) The officer may form the necessary belief during or after an inspection or
independently of an inspection.
(4) The officer may enter the vehicle for the purpose of or in connection with conducting the search.
(5) The officer may exercise powers under this section at any time, and without the consent of the driver or other person apparently in charge of the vehicle or any other person.
(6) Without limiting the above, the power to search a vehicle under this section includes any or all of the following:
(a) the power to search for evidence of an Australian road law offence or a breach of an approved road transport compliance scheme;
(b) the power to search for and inspect any records, devices or other things that relate to the vehicle or any part of its equipment or load and that are located in or on the vehicle;
(c) the power to take copies of or extracts from any or all of the following:
(i) any records that are located in or on the vehicle and that are required to be carried in or on the vehicle under an Australian road law or under an approved road transport compliance scheme;
(ii) any transport documentation or journey documentation located in or on the vehicle;
(iii) any other records, or any readout or other data obtained from any device or thing, located in or on the vehicle that the officer believes on reasonable grounds provide, or may on further inspection provide, evidence of an Australian road law offence or a breach of an approved road transport compliance scheme;
(d) any powers that may be exercised during an inspection of a vehicle under section 40Q(5).
(7) The power to search a vehicle under this section does not include a power to search a person.
(8) The officer may seize and remove any records, devices or other things from the vehicle that the officer believes on reasonable grounds provide, or may on further inspection provide, evidence of an Australian road law offence or a breach of an approved road transport compliance scheme.
(9) The officer may use reasonable force in the exercise of powers under this section.