Research study
How California enforces its ADU law against cities — and what we could not retrieve
We set out to compile every HCD letter of findings against a non-compliant ADU ordinance. HCD’s website was unreachable for two consecutive sessions. This is the honest page: the machinery, the one action that is on the public record, and exactly what failed.
Written by HyreADU Research Desk Primary-source research and data analysis
Audited by HyreADU Research Desk Retrieval audit and scope-of-claim review
What this page is, and what it is not
California’s ADU statute contains an unusually sharp enforcement mechanism, and almost nobody describes it accurately. Government Code section 66316 provides that where a local agency has an ADU ordinance “that fails to meet the requirements of this article, that ordinance shall be null and void and that agency shall thereafter apply the standards established in this article”.
That is voiding by operation of law, not by a decision anybody has to make. Section 66326 adds a review loop with deadlines. An agency must submit an adopted ordinance to the Department of Housing and Community Development “within 60 days after adoption”; HCD may issue written findings of non-compliance; the agency then has “a reasonable time, no longer than 30 days, to respond”.
Failure results in notification to the Attorney General. Since 1 January 2026 the deadlines themselves bite: SB 9 (Arreguín, Stats. 2025, Ch. 510) made a missed 60-day or 30-day deadline void the ordinance outright, with no finding about its content required.
What we could not do, and why this page is shorter than it was designed to be. hcd.ca.gov returned HTTP 403 on every attempt on 2026-09-05, and not one review letter was retrieved.
We are not going to describe, count or characterize documents we could not open.
One ADU enforcement action is on the public record and retrievable: the California Attorney General’s office publishes “Filing a lawsuit against the City of Huntington Beach” for “violating state housing laws by banning the processing applications under SB 9 and applications for accessory dwelling units.” So this page publishes the machinery and the gap — the machinery quoted from the statute, the gap logged with dates and HTTP status codes.
Read this first
- No city is named here as non-compliant
Whether a particular ordinance complies with the ADU article is a legal conclusion, and reaching it is HCD’s job and a court’s job. We publish the mechanism, quote the statute, and quote the state’s own description of its own enforcement action.
We do not add a judgment of our own about any jurisdiction, and we publish no list of “non-compliant cities” — because we could not retrieve the findings that would be the only defensible basis for one.
- The compilation this page was designed around could not be built
HCD’s letters of findings on ADU ordinances are public and are scattered across correspondence files. Compiling them, categorising the flagged provisions and tracking each jurisdiction forward is the study this page was commissioned as.
It did not happen: hcd.ca.gov returned HTTP 403 on every request on 2026-09-05, including a deliberate retry, and on every request throughout the preceding working session. The full log is below.
- A finding is HCD’s position, not a court judgment
Section 66326 lets the department “provide written findings” that an ordinance does not comply, and gives the agency a right to respond — including by adopting the ordinance with findings explaining why it believes it does comply.
That is a disagreement between two public bodies, not an adjudication. Any future edition of this page that does compile the letters will report disputes alongside findings, because the statute contemplates them.
- Public bodies only
This page names cities, counties and state agencies. It names no private individual and no private business, and nothing here is about anyone’s conduct in a private capacity.
- Not legal advice, and the section numbers are new
This is a description of statutory text as retrieved on 5 September 2026. It does not tell you whether any clause in your city’s code is enforceable on your lot.
And the numbers are recent: the ADU article moved out of § 65852.2 into Chapter 13 on 25 March 2024, and was renumbered again inside that chapter on 1 January 2026. Most published guidance is behind one or both.
The machinery, quoted rather than paraphrased
Most descriptions of California ADU enforcement say something like “HCD reviews local ordinances and can find them non-compliant”. That is true and it understates the mechanism substantially, because the strongest provision does not require HCD to do anything at all.
Section 66316, quoted in full as retrieved: “An existing accessory dwelling unit ordinance governing the creation of an accessory dwelling unit by a local agency or an accessory dwelling ordinance adopted by a local agency shall provide an approval process that includes only ministerial provisions for the approval of accessory dwelling units and shall not include any discretionary processes, provisions, or requirements for those units, except as otherwise provided in this article. If a local agency has an existing accessory dwelling unit ordinance that fails to meet the requirements of this article, that ordinance shall be null and void and that agency shall thereafter apply the standards established in this article for the approval of accessory dwelling units, unless and until the agency adopts an ordinance that complies with this article.”
HYRE analysis, and it is the point of this section. That sentence does not say a non-compliant ordinance may be voided, or will be voided if HCD says so.
It says it “shall be null and void”, and that the agency “shall thereafter apply the standards established in this article”.
The default when a local ordinance fails is that state standards apply — automatically, in the drafting.
Whether a given ordinance has failed is of course the contested part, and that is a legal question this page does not answer for any city.
Section 66326 is the review loop: submission “within 60 days after adoption”, the department’s discretion to “provide written findings” that the ordinance does not comply, and “a reasonable time, no longer than 30 days, to respond”, with the agency able to amend or to adopt with contrary findings.
Failure to comply results in notification to the Attorney General, which is how the machinery connects to litigation.
And section 66325 sets the preemption baseline: the article supersedes a conflicting local ordinance, while leaving local agencies free to adopt less restrictive requirements. That asymmetry — cities may be more permissive, never less — is what makes the null-and-void default coherent.
Every enforcement provision, with its current section number
The section numbers here are the ones operative from 1 January 2026. They will not match most published ADU guidance, and that mismatch is itself part of the enforcement problem.
| Provision | What the statute says | Section | Enacted or amended by |
|---|---|---|---|
| Ministerial-only approval, and automatic voiding of a non-compliant ordinance | “shall provide an approval process that includes only ministerial provisions … If a local agency has an existing accessory dwelling unit ordinance that fails to meet the requirements of this article, that ordinance shall be null and void and that agency shall thereafter apply the standards established in this article … unless and until the agency adopts an ordinance that complies.” | § 66316 | Added by Stats. 2024, Ch. 7, Sec. 20 (SB 477), effective 25 March 2024. Retrieved 2026-09-05. |
| Submission to HCD | “within 60 days after adoption” | § 66326(a) | Amended by Stats. 2025, Ch. 510, Sec. 1 (SB 9, Arreguín), effective 1 January 2026. Retrieved 2026-09-05. |
| HCD written findings of non-compliance | The department may provide written findings that the ordinance does not comply. | § 66326(b) | Same. Retrieved 2026-09-05. |
| The agency’s right to respond | “a reasonable time, no longer than 30 days, to respond”; the agency may amend the ordinance, or adopt it with findings explaining why it complies. | § 66326(b) | Same. This is why an HCD finding is a position rather than an adjudication. Retrieved 2026-09-05. |
| Automatic voiding on a missed deadline | Failure to submit within 60 days, or to respond within 30 days, renders the ordinance null and void — with no finding about content required. | § 66326 | Added by SB 9 (Arreguín), Stats. 2025, Ch. 510, effective 1 January 2026. The newest and most procedurally sharp provision on this page. |
| Referral to the Attorney General | Failure to comply results in notification to the Attorney General. | § 66326 | The bridge from administrative review to litigation. Retrieved 2026-09-05. |
| State supersession, one way only | “this article shall supersede a conflicting local ordinance … This article does not limit the authority of local agencies to adopt less restrictive requirements for the creation of an accessory dwelling unit.” | § 66325 | Part of Chapter 13 as created by SB 477. Retrieved 2026-09-05. |
| Application to charter cities | The chapter applies to a charter city notwithstanding Government Code § 65803. | § 66312 | The provision that stops the machinery stopping at a charter city’s boundary. How it interacts with a particular charter is a legal question. |
The citation problem is an enforcement problem. A municipal code that cites § 65852.2, a planning handout that cites § 66324, and a staff report that cites § 66332 are all citing repealed section numbers — § 65852.2 since 25 March 2024, and the others since 1 January 2026.
That does not by itself make an ordinance non-compliant. It does mean that the documents a counter clerk and an applicant are both reading may describe a statute that no longer exists in that form.
The one ADU enforcement action on the retrievable public record
Quoted from the California Attorney General’s own housing page, retrieved 5 September 2026. This is the state describing its own action, and it is the only ADU-specific item on that page.
What the Attorney General says it did
The page lists, among the office’s housing enforcement work, “Filing a lawsuit against the City of Huntington Beach” for “violating state housing laws by banning the processing applications under SB 9 and applications for accessory dwelling units.”
That is the whole of what the page states about it. It gives no outcome and no current status, and we are not going to supply either from memory or inference.
What it establishes is that the referral route in § 66326 is not theoretical: the state has sued a city over ADU application processing, and says so on its own website.
Who does the enforcing
The office describes its Housing Justice Team as “comprised of deputy attorneys general with a broad range of expertise in housing, consumer protection, tenants’ rights, land use, environmental justice, and civil rights.”
Its stated functions include that it “[e]nforces state housing and development laws in the Attorney General’s independent capacity and on behalf of DOJ’s client agencies including the California Department of Housing and Community Development”, and that it “[i]ssues guidance letters to local governments on state housing laws”. Both quotations are verbatim from that page as retrieved on 2026-09-05.
Two things follow. The Attorney General can act in its own right as well as on HCD’s referral — so the § 66326 ladder is not the only route to litigation.
And guidance letters to local governments are a second body of public correspondence, separate from HCD’s ordinance-review letters, that a future edition of this study should also compile.
What we are careful not to say
We do not say the City of Huntington Beach’s ADU ordinance is non-compliant. That is the state’s allegation in litigation, and an allegation is not a determination.
We do not say this is the only ADU enforcement action in California. It is the only one on the page we were able to retrieve, on the date we retrieved it. HCD’s own correspondence — the larger body of enforcement activity — was unreachable, which is precisely the gap this page is about.
One adjacent observation, offered carefully
Separately from the enforcement record, HCD’s Annual Progress Report data contains its own weak signal about jurisdictions whose ADU administration is unusual. 4 jurisdictions in Table A2 report substantial ADU permits and literally zero ADU completions across multiple reporting years.
Fact. Those four are Huntington Beach (495 ADU permits reported across 7 years, zero completions in every year); Saratoga (467 ADU permits reported across 8 years, zero completions in every year); West Sacramento (65 ADU permits reported across 6 years, zero completions in every year); Arvin (42 ADU permits reported across 4 years, zero completions in every year).
We exclude them from ratio work in our production studies under a published rule, and we name them there too.
One of them is the jurisdiction the Attorney General sued. Huntington Beach reported 495 ADU permits and zero ADU completions between 2018 and 2025.
Our own note on the exclusion records that its “[c]ompletion fields for ADUs are unused across multiple reporting years” and that it “also reported zero certificates of occupancy for every other housing type”.
HYRE analysis, and the caution matters more than the observation. Zero completions across every housing type is a reporting-practice fact, not a building fact — it is far more likely that the certificate-of-occupancy fields were never filled in than that no home was finished in the city for eight years.
It is not evidence of ordinance non-compliance, it is not what the Attorney General sued about, and we are not asserting a connection between the two.
What it is: a reminder that a jurisdiction’s relationship with state housing reporting and its relationship with state housing law are administered by the same people, and that both are visible in public data if anyone looks.
A further 15 jurisdictions report zero ADU completions below our exclusion threshold. We do not name them as a group here, because below the threshold the zero is much more likely to be a small jurisdiction with genuinely few completions than a reporting failure, and a list would imply otherwise.
The retrieval log
Published in full, with dates and outcomes. A gap that is documented can be closed by someone else; a gap that is quietly papered over cannot.
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2026-09-05 — failed
hcd.ca.gov — HTTP 403 ForbiddenRequested the department’s accessory dwelling unit policy page. The server returned HTTP 403 and no response body. This was a deliberate retry of a request that had returned 403 repeatedly throughout the preceding working session. Consequence: no HCD-hosted document — no review letter, no technical-assistance memorandum, no Handbook edition — was opened for this study.
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2026-09-05 — succeeded
leginfo.legislature.ca.gov — Government Code §§ 66316, 66325, 66326The Legislative Counsel’s own codes service returned full operative text with amendment history for each section. Every statutory quotation on this page comes from these retrievals and is quoted rather than paraphrased.
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2026-09-05 — succeeded
oag.ca.gov/housing — California Attorney GeneralReturned the Housing Justice Team description and the list of housing enforcement actions, including the single ADU-specific item quoted above. A follow-up request to oag.ca.gov/housing/actions returned HTTP 404, so no per-action detail page was retrieved and no docket number, filing date or outcome is published here.
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2026-09-05 — succeeded
data.ca.gov — HCD Annual Progress Report dataThe department’s own data, published on the California open data portal, was reachable throughout. This is why our production studies could be built while this enforcement study could not: the data is on a different host from the documents.
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2026-09-05 — unavailable
Web searchThe session’s web-search budget was fully consumed (200 of 200 calls) before this study began, so no search-driven discovery of individual review letters was possible. Retrieval was limited to URLs that could be constructed directly.
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Preceding session — failed
library.municode.com and city code mirrorsAutomated requests to municode returned HTTP 403 for every jurisdiction attempted, and the elaws.us mirrors timed out. Codified municipal ADU text remains largely unreachable to this desk by automated retrieval, which is a standing obstacle to the ordinance-tracking half of this study and not specific to this page.
If you are reading this and can supply HCD’s ADU ordinance-review correspondence in a machine-readable form — or can confirm where it is published — that is the single input that turns this page into the study it was designed to be.
What a complete edition would contain
What we would compile
Every HCD letter of findings on an ADU ordinance, with the jurisdiction, the date, and the specific provisions the department flagged.
A coding of those provisions into categories — owner-occupancy, size, setback, parking, discretionary review, fee, design standards — so that the recurring failure modes can be counted rather than anecdoted.
The jurisdiction’s response: amended, adopted with contrary findings, or no response on the record. And the elapsed time between the finding and the amendment where one occurred.
The Attorney General’s guidance letters to local governments, which the office says it issues and which are a second, separate correspondence trail.
What we would still refuse to publish
A verdict that any named jurisdiction’s ordinance is unlawful. HCD’s finding is HCD’s position; the statute expressly allows an agency to disagree in writing; and a court decides.
A ranking of cities by non-compliance. The letters are not distributed evenly because the underlying ordinances are not equally scrutinised, and a league table would measure attention as much as conduct.
Any inference from silence. A jurisdiction with no letter may have a compliant ordinance, or may simply not have been reviewed.
Anything about a private individual. This subject is about public bodies and it stays that way.
Terms, used precisely
- Letter of findings
- HCD’s written statement, under Gov. Code § 66326, that a submitted ordinance does not comply with the ADU article. A position taken by a state department, which the local agency has a statutory right to answer. Not a court judgment and not a penalty.
- Null and void
- The statutory consequence in § 66316 of an ADU ordinance that fails the article’s requirements: the ordinance ceases to have effect and the agency applies the state standards instead, by operation of law rather than by anyone’s decision.
- Ministerial approval
- Approval against objective standards, without discretionary review or a hearing. § 66316 requires an ADU ordinance to provide only ministerial provisions, which is why a discretionary design review of an ADU is the classic non-compliance question.
- Supersession
- Under § 66325 the state article overrides a conflicting local ordinance — but only in one direction. A local agency remains free to adopt less restrictive ADU requirements than the state minimum.
- SB 9 — two different statutes
- SB 9 (Atkins), Stats. 2021, Ch. 162 is the urban lot-split law. SB 9 (Arreguín), Stats. 2025, Ch. 510 is the ADU ordinance-review amendment described on this page. They share a bill number across different sessions and are routinely confused.
Questions
What happens if a city’s ADU ordinance does not comply with state law?
Does HCD have to find an ordinance non-compliant before it is void?
Can I see the list of California cities HCD has found non-compliant?
Has the state ever actually sued a city over ADUs?
Who enforces state ADU law — HCD or the Attorney General?
My city’s code still has an owner-occupancy requirement. Is it void?
Why do the section numbers here not match what my city’s code says?
When will you publish the compiled letters?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of Government Code §§ 66316, 66325 and 66326 retrieved from leginfo.legislature.ca.gov 2026-09-05; California Attorney General housing enforcement page retrieved 2026-09-05; HCD Housing Element Annual Progress Report data retrieved from data.ca.gov 2026-09-05. hcd.ca.gov itself: HTTP 403 on every attempt, 2026-09-05.. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- California Government Code § 66316 — ministerial approval, and a non-compliant ADU ordinance is null and void , Quoted in full on this page as retrieved: “An existing accessory dwelling unit ordinance … shall provide an approval process that includes only ministerial provisions … If a local agency has an existing accessory dwelling unit ordinance that fails to meet the requirements of this article, that ordinance shall be null and void and that agency shall thereafter apply the standards established in this article for the approval of accessory dwelling units, unless and until the agency adopts an ordinance that complies with this article.” History as retrieved: “Added by Stats. 2024, Ch. 7, Sec. 20. (SB 477) Effective March 25, 2024.” Retrieved 2026-09-05.
- California Government Code § 66326 — submission of ADU ordinances to HCD, findings, and response , Retrieved in full. Requires submission “within 60 days after adoption”; the department may provide written compliance findings; the agency receives “a reasonable time, no longer than 30 days, to respond”; the agency may amend the ordinance or adopt it with explanatory findings; failure results in notification to the Attorney General; a non-compliant ordinance becomes “null and void”. History as retrieved: “Amended by Stats. 2025, Ch. 510, Sec. 1. (SB 9) Effective January 1, 2026.” Retrieved 2026-09-05.
- California Government Code § 66325 — the state article supersedes a conflicting local ordinance , The one-directional preemption baseline: the article supersedes a conflicting local ordinance, and does not limit local authority to adopt less restrictive ADU requirements. Retrieved 2026-09-05.
- SB 9 (Arreguín, 2025) — Accessory dwelling units: ordinances. Stats. 2025, Ch. 510 , Chaptered 10 October 2025, effective 1 January 2026. The amendment that makes a missed 60-day submission or 30-day response void the ordinance. Distinct from SB 9 (Atkins), Stats. 2021, Ch. 162, the urban lot-split statute — a confusion this page flags explicitly. Retrieved 2026-09-05.
- SB 477 (2024) — recodification of the ADU provisions. Stats. 2024, Ch. 7 , The urgency statute, effective 25 March 2024, that repealed Government Code §§ 65852.150, 65852.2, 65852.22, 65852.23 and 65852.26 and created Chapter 13 (§§ 66310–66342), including § 66316. Retrieved 2026-09-05.
- California Attorney General — housing enforcement and the Housing Justice Team , Retrieved 2026-09-05. Quoted verbatim on this page: the Housing Justice Team is “comprised of deputy attorneys general with a broad range of expertise in housing, consumer protection, tenants’ rights, land use, environmental justice, and civil rights”; it “[e]nforces state housing and development laws in the Attorney General’s independent capacity and on behalf of DOJ’s client agencies including the California Department of Housing and Community Development”; and it “[i]ssues guidance letters to local governments on state housing laws”. The single ADU-specific action listed: “Filing a lawsuit against the City of Huntington Beach” for “violating state housing laws by banning the processing applications under SB 9 and applications for accessory dwelling units.” A follow-up request to /housing/actions returned HTTP 404 and no per-action detail was retrieved. Retrieved 2026-09-05.
- California HCD — Housing Element Annual Progress Report data (data.ca.gov) , The source of the reporting-practice observation on this page. 922,102 Table A2 rows; 4 jurisdictions report at least 40 ADU permits across at least three years with zero ADU completions in every year. Retrieved 2026-09-05; publisher timestamp 2026-09-04T15:44:00Z. Note that this is HCD’s data on a different host from hcd.ca.gov, which is why it was reachable when the department’s own site was not. Retrieved 2026-09-05.
Ask which standards your agency will apply, in writing
Where a local ordinance and the state article disagree, the mechanism is statutory but the answer on your lot comes from the counter. Asking in writing which standards will be applied is the single most useful thing a homeowner can do with this page.
HyreADU does not design, permit or build accessory dwelling units and does not practice law. This page is informational and is not legal advice.
It describes California statutory text as retrieved from the Legislative Counsel’s service on 5 September 2026 and quotes state agencies’ own published words; it does not tell you whether any provision of any municipal code is enforceable on any property, and it names no jurisdiction as non-compliant.
An HCD finding is a state department’s position, which the statute expressly permits a local agency to dispute in writing; an allegation in litigation is not a determination. Only public bodies are named on this page.
hcd.ca.gov returned HTTP 403 on every attempt on 5 September 2026, including a deliberate retry, and no HCD-hosted document was opened for this study — the full retrieval log is published above, and the compilation of ordinance-review letters this page was designed around remains outstanding.
Statutes change, and this one has been renumbered twice since March 2024.