(a) Notwithstanding any other law, and except as otherwise provided in subdivision (b), a local agency shall not deny a permit for an unpermitted accessory dwelling unit or an unpermitted junior accessory dwelling unit that was constructed before January 1, 2020, due to either of the following:

1. (1) The accessory dwelling unit or junior accessory dwelling unit is in violation of building standards pursuant to Article 1 (commencing with Section 17960) of Chapter 5 of Part 1.5 of Division 13 of the Health and Safety Code.
2. (2) The accessory dwelling unit or junior accessory dwelling unit does not comply with this article or Article 3 (commencing with Section 66333), as applicable, or any local ordinance regulating accessory dwelling units or junior accessory dwelling units.

(d) A local agency shall inform the public about the provisions of this section through public information resources, including permit checklists and the local agency’s internet website, which shall include both of the following:

1. (1) A checklist of the conditions specified in Section 17920.3 of the Health and Safety Code that would deem a building substandard.
2. (2) Informing homeowners that, before submitting an application for a permit, the homeowner may obtain a confidential third-party code inspection from a licensed contractor to determine the unit’s existing condition or potential scope of building improvements before submitting an application for a permit.