Brunei's CPTPP Annex 1 on Non-Conforming Measures lists a series of restrictions that are supposedly reflective of underlying regulations listed in the measures section of the Annex entry. In this case, the Brunei Darussalam's Long-Term Development Plan and Administrative Measures and Guidelines are said to prohibit foreign investors from using land under the control of the  Department of Agriculture, Ministry of Primary Resources and Tourism for any agriculture and services incidental to agricultural activities unless they comply with the specified local content requirements. Based on such entry alone it is unclear what is the scope and format of such restrictions, and the extent to which they actually imply a discriminatory treatment in relation to foreign-owned locally incorporated firms. The actual text of the referred underlying regulations cound not be accessed and verified. 

Brunei Darussalam's latest WTO Trade Policy Review (WTO, 2015) provides additional clarity to the regulatory regime in place: "[...] Full foreign investment may be allowed in most activities, except in those that use natural resources, relate to food security, and are located in industrial sites for which 30% minimum local equity participation is required. [...]  Foreign investment in primary sectors is capped at 70% [...].". Reply by the Bruneian Delegation to questions of WTO members on the occasion of a previous Trade Policy Review in 2008 clarifies the scope of application of local content requirements: "[...] REPORT BY THE SECRETARIAT (WT/TPR/S/196) Summary Observations; (5) Outlook; Page xiii, Paragraph 27: The Secretariat Report notes that "Foreign investment policies, while encouraging investment in all sectors, are unclear about limits on foreign equity holdings and the sectors in which investment is restricted" [...]. Answer: (b) Brunei Darussalam does not have a list. However, under the ASEAN Investment Area Bold Measures Agreement signed in January 1999, Brunei Darussalam allows for 100% foreign equity ownership in high-technology manufacturing and export oriented industries. Other than that, full foreign ownership is not permitted in sectors involving local natural resources (notably fisheries and agriculture) and those relating to national food security where a minimum of 30% local participation is required. [...]" (WTO, 2008).

Therefore, for the OECD FDI Regulatory Restrictiveness Index, it is assumed that foreign investment in agriculture, forestry, fisheries, mining and electricity generation is subject to joint venture with local equity partners. 
"ANNEX I - SCHEDULE OF BRUNEI DARUSSALAM
Sector: Agriculture and Services Incidental to Agriculture
Obligations Concerned: Performance Requirements (Article 9.10)
Measures: Brunei Darussalam Long-Term Development Plan, Administrative Measures and Guidelines
[...] 
Description: Investment […]
Foreign investors may not utilise sites under the control of the Department of Agriculture, Ministry of Primary Resources and Tourism, for any agriculture and services incidental to agriculture activities unless they comply with these requirements: (a) to purchase, use or accord a preference to goods produced in Brunei Darussalam, or to purchase goods from local suppliers; (b) to achieve a given level or percentage of domestic content; or (c) to transfer technology or other proprietary knowledge to persons in Brunei Darussalam, as long as such requirement to transfer technology or other proprietary knowledge does not unreasonably prejudice the legitimate interests of the owner of technology or proprietary knowledge and is not for the purposes of commercial exploitation by Brunei Darussalam.” (ANNEX I - SCHEDULE OF BRUNEI DARUSSALAM, Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP))
ANNEX I - SCHEDULE OF BRUNEI DARUSSALAM, Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP)
[<a href="https://www.mfat.govt.nz/assets/Trade-agreements/TPP/Annexes-ENGLISH/Annex-I.-Brunei.pdf">CPTPP</a>],[<a href="https://docs.wto.org/dol2fe/Pages/FE_Search/FE_S_S006.aspx?Query=((%20@Title=%20brunei%20darussalam)%20or%20(@CountryConcerned=%20brunei%20darussalam))%20and%20(%20(%20@Symbol=%20wt/tpr/s/*%20)%20or%20(%20@Symbol=%20wt/tpr/m/*%20not%20add*)%20or%20(%20@Symbol=%20wt/tpr/m/*%20and%20add*))&Language=ENGLISH&Context=FomerScriptedSearch&languageUIChanged=true#">Other</a>],[<a href="https://docs.wto.org/dol2fe/Pages/FE_Search/FE_S_S006.aspx?Query=((%20@Title=%20brunei%20darussalam)%20or%20(@CountryConcerned=%20brunei%20darussalam))%20and%20(%20(%20@Symbol=%20wt/tpr/s/*%20)%20or%20(%20@Symbol=%20wt/tpr/m/*%20not%20add*)%20or%20(%20@Symbol=%20wt/tpr/m/*%20and%20add*))&Language=ENGLISH&Context=FomerScriptedSearch&languageUIChanged=true#">Other</a>]