Picture a fourplex on an ordinary residential lot. The city’s zoning code says the project needs a set number of parking spaces per unit. A state statute passed a year or two later says the city can no longer require that many, and near transit may not be able to require any at all. Both documents are written in plain English. Both use the word “required.” Only one of them controls.
That gap between what a code says and what the law is has become one of the defining features of land-use practice. It is also where a lot of the housing this country needs is quietly won or lost.
Industry news: the state layer is moving
According to the National Association of Counties, 511 bills with clauses preempting county land-use authority were introduced across 40 states in 2025, and roughly three out of four sought to override or significantly constrain local authority. That count covers county authority alone. Cities have seen their own wave.
The reason is not hard to find. Estimates of the national housing shortfall run from roughly 2 million homes to well over 4 million, depending on who is counting. NAHB’s 2026 study found that regulation accounts for 26.4 percent of the price of a new single-family home. That cost is not idle money. It is absorbed by process, delay, and compliance before the first family moves in. When local decisions keep producing that result, legislatures step in on parking, lot sizes, middle housing, ADUs, and permit timelines.
The federal government is pushing as well, in a different way. The ROAD to Housing Act does not rewrite a single zoning map. It changes the financial incentives around federal funding and directs HUD to publish zoning best practices. The rules themselves still land locally, one code amendment at a time.
The result is a legal environment where a single parcel can be shaped by four levels of government at once, each moving on its own timeline.
What does “authority level” mean in zoning?
Authority level is the level of government a rule comes from. It determines how much weight that rule carries when it meets a rule from another level.
- City. Most day-to-day zoning lives here: districts, uses, setbacks, height, parking, and the hearing process.
- County. In many states, counties regulate land use in unincorporated areas. A parcel annexed last year may have moved from one rulebook to another.
- State. States set the framework local governments work within, and they are increasingly writing housing rules directly.
- Federal. Federal law rarely writes zoning, but it overlays specific subjects such as fair housing, religious land uses, and floodplain management tied to the National Flood Insurance Program. It also shapes local choices through funding.
Who decides how much power a city has?
Underneath every preemption question is an older one: where does local power come from in the first place? Two traditions answer it differently.
Under Dillon’s Rule, named for an Iowa judge in the 1860s, local governments hold only the powers the state expressly grants them, plus those necessarily implied. Under Home Rule, local governments have broad authority over local matters unless the state has limited it. Many states blend the two, applying different approaches to different kinds of local government or different subjects.
This matters in practice. In a Dillon’s Rule setting, the first question about an unusual local requirement may be whether the city had the authority to adopt it at all. In a Home Rule setting, the question is more often whether a state law has since taken that authority back.
How can the same word carry different law?
Zoning vocabulary is shared across every level of government, and that is exactly the trap. A few examples land-use professionals will recognize:
- Parking “required.” A city’s parking minimum may now sit beneath a state cap or a state exemption near transit. The local number is still printed. It may no longer apply as written.
- Accessory dwelling unit. States including Washington and California have written their own ADU rules, covering questions like owner occupancy and parking. A conflicting local rule may be superseded even if the code was never amended.
- Setback. The same word, measured the same way, can carry a different number under the county code that governed a parcel last year and the city code that governs it after annexation.
Every one of these words also has a date attached. The rule that applied when an application was filed may not be the rule that applies today, and it may not be the rule that applies after the next legislative session.
Why does blending the layers go wrong?
Most research errors in this area are not errors of reading. They are errors of layering. Reading the city code carefully and missing the state statute on top of it. Relying on a summary that merges city and county rules into a single answer. Checking the current code when the real question is what applied on the date an application was filed.
The legal AI field has been learning the same lesson in public. The cases where tools produced confident, unsupported answers have become a curriculum: tie every statement to its source, keep track of which authority and which date it came from, use careful language where a question is unresolved, and keep a qualified professional in the loop. That discipline is not a reason to avoid technology. It is the standard technology has to meet.
Why does this matter for affordable housing?
Here is the part that does not get said enough. State housing reforms only produce housing when someone carries them into the room where the local decision gets made.
A legislature can cap parking minimums. It can require cities to allow duplexes and fourplexes. It can set deadlines for permit decisions. But if the local code still reads the old way, and nobody at the counter or the hearing points to the state law, the old rule tends to win by default. The applicant redesigns, adds parking, drops a unit, or walks away. The cost gets absorbed. The home does not get built.
The land-use professional is often the person in the best position to close that gap. Knowing which level of government controls is not academic. It is how a fourplex stays a fourplex.
Trent’s take
I spent years testifying about data in federal and state courts, and the lesson that carried over is simple: an answer is only as good as the record behind it. Zoning is no different. Most of the time, finding the law is not the hard part. Knowing which law, from which level of government, as of which date, is.
Cities have had decades to solve the housing problem through local codes, and the numbers say that approach has not kept up. States are now moving, and the federal government is putting money behind it. I do not think that makes local land-use work less important. I think it makes it more important. The professionals who can read all four layers at once, and explain them in plain terms to a client, a planner, and a hearing examiner, are the ones who will turn these reforms into actual homes.
This is chess, not poker. You win by knowing the board.
Discussion questions
- When a state housing law and a local code disagree, who usually raises it first in your experience: planning staff, the applicant, or the hearing body?
- Which level of authority is hardest to track in your jurisdiction right now, and why?
The board is changing
None of this happens at the federal level alone. It happens in thousands of city and county code amendments, each on its own timeline, each with its own hearing record. Knowing the law as it stands today, as it stood when a client’s application was filed, and as it is about to change is the whole job.
That is the problem we set out to solve at ZoneLex. We are building a jurisdiction-aware foundation for U.S. land use with one goal: helping land-use professionals spend less time digging through layers and more time getting housing approved.
ZoneLex does the digging. The attorney does the dealmaking.
Sources:
State Policy Trends: Land Use Preemption, National Association of Counties →
Government Regulation in the Price of a New Home: 2026, NAHB →
Home Building Regulatory Cost Burdens Increased 40% from 2021 to 2026, NAHB Eye on Housing →
21st Century ROAD to Housing Act, Public Law 119-101 (July 11, 2026)