Under the Foreign Acquisitions and Takeovers Act 1975, certain 'significant actions' can be prohibited by the Treasury if considered to be contrary to the 'national interest'. Proposed investments in agricultural land by foreign persons generally constitute a significant action if the cumulative value of a foreign person's agricultural land holdings exceeds a specific monetary threshold. Such investments must be notified to the Treasury before the action can be taken.  A higher monetary threshold applies to investors from specified trade agreement partner countries. Agricultural land is defined in the Act as land in Australia that is used, or that could reasonably be used, for a primary production business. The documents of the Foreign Investment Review Board give further guidance as to what the concept of agricultural land covers (see Foreign Investment Review Board, Guidance note 17 - Agricultural land investments, last updated 24 April 2020, pp. 6-10).
The national interest, and what would be contrary to it, is not defined in the Act or the Foreign Acquisitions and Takeovers Regulation 2015. Assessments are made on a case-by-case basis. However, a Foreign Investment Policy document states that the Government typically considers the following factors when assessing foreign investment proposals: national security; competition; other Australian government policies, including tax; impact on the economy and the community and the character of the investor. In the case of acquisitions of an interest in agricultural land that will be used for a primary production business or residential development, the national interest test includes a consideration of whether there was an opportunity for Australian investors to acquire the given parcel of agricultural land or agricultural land entity, as well a the openness and transparency of the sale process.
"4 Dictionary of definitions
 In this Act: [...]
agricultural land means land in Australia that is used, or that could reasonably be used, for a primary production business [...]
Australian land means agricultural land, commercial land, residential land or a mining or production tenement. [...]
foreign person means:
 (a) an individual not ordinarily resident in Australia; or
 (b) a corporation in which an individual not ordinarily resident in Australia, a foreign corporation or a foreign government holds a substantial interest; or
 (c) a corporation in which 2 or more persons, each of whom is an individual not ordinarily resident in Australia, a foreign corporation or a foreign government, hold an aggregate substantial interest; or
 (d) the trustee of a trust in which an individual not ordinarily resident in Australia, a foreign corporation or a foreign government holds a substantial interest; or
 (e) the trustee of a trust in which 2 or more persons, each of whom is an individual not ordinarily resident in Australia, a foreign corporation or a foreign government, hold an aggregate substantial interest; or
 (f) a foreign government; or
 (g) any other person, or any other person that meets the conditions, prescribed by the regulations.
[...]
12 Meaning of interest in Australian land
 (1) An interest in Australian land (however described) is:
 (a) a legal or equitable interest in Australian land, other than:
 (i) an interest under a lease or licence or in a unit in a unit trust; or
 (ii) an interest in an agreement giving a right (known as a profit à prendre) to take something off another person's land, or to take something out of the soil of that land; or
 (iii) an interest in an agreement involving the sharing of profits or income from the use of, or dealings in, Australian land; or
 (b) an interest in a security in an entity that owns Australian land, being a security that entitles the holder to a right to occupy a dwelling of a kind known as a flat or home unit situated on the land; or
 (c) an interest as lessee or licensee in a lease or licence giving rights to occupy Australian land if the term of the lease or licence (including any extension or renewal) is reasonably likely, at the time the interest is acquired, to exceed 5 years; or
 (d) an interest in an agreement giving a right of a kind mentioned in subparagraph (a)(ii) if the term of the agreement (including any extension or renewal) is reasonably likely, at the time the interest in the agreement is acquired, to exceed 5 years; or
 (e) an interest in an agreement involving the sharing of profits or income from the use of, or dealings in, Australian land if the term of the agreement (including any extension or renewal) is reasonably likely, at the time the interest in the agreement is acquired, to exceed 5 years; or
 (f) an interest in a share in an Australian land corporation or agricultural land corporation; or
 (g) an interest in a unit in an Australian land trust or agricultural land trust; or
 (h) if the trustee of an Australian land trust or agricultural land trust is a corporation—an interest in a share in that corporation.
 (2) An interest is an interest in Australian land even if it is the only interest that exists in the land or other thing concerned.
 (3) A person acquires an interest in Australian land even if:
 (a) the person has previously acquired an interest in Australian land; or
 (b) the interest is an increase in the amount of an existing interest of the person in Australian land.
[...]
43 Meaning of significant action—land
 An action is a significant action if:
 (a) the action is for a foreign person to acquire an interest in Australian land; and
 (b) the threshold test is met in relation to the land (see Subdivision B of Division 4).
44 Meaning of significant action—actions prescribed by the regulations
 (1) The regulations may provide that a specified action is a significant action (including by providing that a specified action is a significant action if specified conditions are met).
 (2) Sections 40, 41 and 43 do not limit the actions that may be specified by the regulations.
[...]
47 Meaning of notifiable action—general
 (1) An action is a notifiable action if the conditions in this section are met.
First condition—kinds of action
 (2) The first condition is that the action is any of the following:  [...]
 (c) to acquire an interest in Australian land.
Second condition—threshold
 (3) The second condition is that the threshold test is met in relation to the entity, business or land (see Subdivision B of Division 4).
Third condition—kinds of entities covered
 (4) If paragraph (2)(a) or (b) applies, the third condition is that the entity is: [...]
Last condition—action taken by a foreign person
 (5) The last condition (whether paragraph (2)(a), (b) or (c) applies) is that the action is or is to be taken by a foreign person.
48 Meaning of notifiable action—actions prescribed by the regulations
 (1) The regulations may provide that a specified action is a notifiable action (including by providing that a specified action is a notifiable action if specified conditions are met).
 (2) Section 47 does not limit the actions that may be specified by the regulations.
[...]
52 The threshold test for land [...]
Agricultural land where total value of interests is above threshold value
 (2) The threshold test is met in relation to land if both of the following apply:
 (a) the land is agricultural land;
 (b) the total value of the following is more than the value prescribed for the purposes of this paragraph:
 (i) all interests in agricultural land held by the foreign person, alone or together with one or more associates;
 (ii) the consideration for the acquisition of the interest in the land.
[...]
55 Regulations
 (1) Regulations made for the purposes of this Part may prescribe any of, or any combination of, the following:
 (a) values of nil;
 (b) different values for different kinds of entities, businesses or land;
 (c) different values for different kinds of foreign persons;
 (d) different values for:
 (i) sensitive businesses generally; or
 (ii) different sensitive businesses for different foreign persons.
[...]
67 Order prohibiting proposed significant actions
 (1) The Treasurer may, by notifiable instrument, make an order under subsection (2) if the Treasurer is satisfied that:
 (a) a significant action is proposed to be taken; and
 (b) taking the significant action would be contrary to the national interest.
 (2) The Treasurer may make an order in accordance with the following table.
Powers of Treasurer to prohibit proposed significant actions
Item | If the significant action is ... | the Treasurer may make an order prohibiting ...
1 | to acquire a direct interest in an Australian entity that is an agribusiness, or an interest in securities in an entity | the whole or a part of the proposed acquisition.
2 | to issue securities in an entity | the whole or a part of the proposed issue of the securities. [...]
5 | to acquire a direct interest in an Australian business that is an agribusiness, or an interest in assets of an Australian business | the whole or a part of the proposed acquisition. [...]
8 | to acquire an interest in Australian land | the proposed acquisition.
9 | to take any significant action prescribed by regulations made for the purposes of section 44 | any thing prescribed by regulations made for the purposes of this item.
[...]
81 Compulsory notice of notifiable actions
 (1) A foreign person who proposes to take a notifiable action must give a notice to the Treasurer before taking the action.
 (2) If a person takes an action by entering an agreement, the notice must deal with each notifiable action covered by the agreement.
82 Limitation on taking significant actions after notice given
 (1) This section applies in relation to a foreign person who gives a notice to the Treasurer stating that a significant action (including a significant action that is a notifiable action) is proposed to be taken.
 (2) The foreign person must not take the action before the earliest of the following:
 (a) the day that is 10 days after the end of the decision period mentioned in section 77;
 (b) if an interim order is made—the end of the period specified in the order;
 (c) the day a no objection notification is given to the person.[...] (Foreign Acquisitions and Takeovers Act 1975 (Act No. 92 of 1975), last amended by Australia's Foreign Relations (State and Territory Arrangements) (Consequential Amendments) Act 2020 on 1 January 2021, Sections 4, 12, 43, 44, 47, 48, 52, 55, 67, 81 and 82)
--------------------------
"40 Action relating to agribusinesses and agricultural land for certain investors [...]
Land entities
 (3) A relevant agreement country investor, or an enterprise or national of Thailand (other than a foreign government investor), who takes an action relating to an interest in agricultural land that is used wholly and exclusively for a primary production business may, for the purposes of section 13 of this instrument, disregard the fact that the land is agricultural land.
 (4) To avoid doubt, an action taken in relation to an interest in agricultural land that is used wholly and exclusively for a primary production business includes an action taken by acquiring a security in a land entity that holds agricultural land that is used wholly and exclusively for a primary production business.
[...]
52 Land [...]
Threshold value for agricultural land
 (4) The following table prescribes a value for paragraph 52(2)(b) of the Act (agricultural land).
Threshold value for agricultural land
Item | For this kind of land ... | the value (in millions of dollars) is ...
1 | agricultural land that is being acquired by a foreign person | 15
2 | agricultural land that is held by an agricultural land corporation or an agricultural land trust if the interest that is being acquired by a foreign person is an interest in a share in the corporation or a unit in the trust | 15 [...]" (Foreign Acquisitions and Takeovers Regulation 2015 (SLI 2015 No. 217), last amended by Foreign Investment Reform (Protecting Australia's National Security) Regulations 2020 on 1 January 2021, Sections 40 and 52)
Foreign Acquisitions and Takeovers Act 1975 (Act No. 92 of 1975), last amended by Australia's Foreign Relations (State and Territory Arrangements) (Consequential Amendments) Act 2020 on  1 January 2021, Sections 4, 12, 43, 44, 47, 48, 52, 55, 67, 81 and 82
Foreign Acquisitions and Takeovers Regulation 2015 (SLI 2015 No. 217), last amended by Foreign Investment Reform (Protecting Australia's National Security) Regulations 2020 on 1 January 2021, Sections 40 and 52
[<a href="https://www.legislation.gov.au/Details/C2021C00022/Html/Text">Act</a>],[<a href="https://www.legislation.gov.au/Details/F2021C00062">Reg</a>],[<a href="https://firb.gov.au/sites/firb.gov.au/files/guidance-notes/GN03_Agriculture.pdf">Guidance</a>],[<a href="https://firb.gov.au/sites/firb.gov.au/files/2021-01/Australias_foreign_investment_policy.pdf">Policy</a>]