Deep Research: Supermajority laws around the states

Here are the results of my first use of OpenAI’s Deep Research tool. I asked for information that I know well – and in which inaccurate research has been published. It did a great job and relied substantially on my own research. But it also went beyond my list – identifying protest petition statutes in two states I had missed: New Mexico and South Dakota. That’s embarrassing.

Deep Research also turned up an important, related law I hadn’t known: Downzonings in Wisconsin require a 2/3 majority vote.

Getting the prompt right

First, I asked ChatGPT 4o how to write the prompt.

I’m a land use, housing, and zoning researcher. A key question in my area is how easy or difficult it is to change zoning. In most states, to change the zoning of a particular parcel or the text of a particular zoning district requires a simple majority vote of the city council, town meeting, or other legislative body. I’d like to ask Deep Research to find out which states, if any and under which conditions, require a supermajority vote to change zoning. Can you help me write a prompt to pose this question to Deep Research?

GPT replied:

Here’s a clear and precise prompt for Deep Research:
_______________________________________________________________________
Research Request: Supermajority Requirements for Zoning Changes by State
I’m conducting research on the legal and procedural requirements for zoning changes in different U.S. states. In most states, changing the zoning of a specific parcel or amending the text of a zoning district requires a simple majority vote by the relevant legislative body (e.g., city council, town meeting). However, I am interested in identifying states where a supermajority vote is required under certain conditions.
Please provide:

1. A list of states that require a supermajority vote for zoning changes.
2. The specific conditions under which a supermajority is required (e.g., protests from property owners, changes inconsistent with a comprehensive plan, state-imposed rules).
3. Citations to legal sources (state statutes, case law, municipal codes) supporting these requirements.
4. Any relevant exceptions or nuances, such as different rules for different types of zoning changes (rezoning vs. text amendments).

The research should focus on statutory or widely applied legal requirements rather than isolated municipal rules unless they reflect a statewide policy trend.
_______________________________________________________________________

This should help you get a thorough and well-documented response. Would you like any refinements?

Deep Research clarifies the request

I used that prompt in Deep Research. It asked for clarification before going further:

Your research request is well-structured and clear. To ensure the most comprehensive and useful results, could you clarify:

1. Time Sensitivity: Do you need the most up-to-date legal information as of 2024, or would older sources also be useful?
2 Focus on Specific Government Levels: Are you only interested in state-imposed supermajority requirements, or should we also consider widely adopted municipal policies that indicate a broader trend?
3. Scope of Legal Sources: Should the research include only statutory law and case law, or would administrative rulings and legal interpretations (e.g., attorney general opinions) also be helpful?

Once confirmed, I will begin the research and provide a detailed response.

I replied:

Thanks.

1. Older sources would be more useful, but please confirm if policies have changed since those sources.

2. I’m interested in state-imposed supermajority requirements.

3. Statutes, case law, administrative rulings, and legal interpretations are all helpful.

Deep Research’s output

After eight minutes, Deep Research provided the following, which I will include without indenting.

Supermajority Vote Requirements for Zoning Changes (By State)

Overview: Under many state zoning enabling laws, certain zoning changes (typically rezoning/map amendments) require more than a simple majority vote in the local governing body. The most common trigger is a valid protest petition filed by nearby property owners, which elevates the approval threshold to a supermajority (often two-thirds or three-fourths) (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center) (Memorandum). About 20–22 states have such protest?petition supermajority provisions in state law (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center) (Memorandum). A few states impose supermajority votes in other scenarios (e.g. general state mandates or special cases like downzoning). Below is a list of states with supermajority requirements, the conditions that trigger them, and key legal sources. We also note any major exceptions or recent changes (prioritizing older authority but noting updates).

Protest-Petition Supermajority Requirements

In these states, if a specified percentage of affected property owners formally protest a proposed zoning change, state law requires a supermajority vote of the city council or county board to adopt the change. Absent a valid protest, a simple majority suffices. The typical threshold is 20% of the owners of the land subject to the rezoning or of the immediately adjacent area, but a few states use different percentages (2005-006 | 2/24/2005 | Kansas Attorney General Opinion) (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator). The required supermajority is usually either two-thirds (2/3) or three-fourths (3/4) of the governing body’s members, depending on the state (Memorandum) (Memorandum). (Notably, North Carolina and Wisconsin formerly had protest-petition supermajority rules but have repealed them in recent years (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center) (Zoning FAQ 5 | LWM, WI ).) Key state provisions include:

• Arizona: A protest by owners of 20% of the area within 150 feet of a rezoning triggers a ¾ vote requirement of the city/town council or county board (New Rezoning Protest Law: Game-Changer for Controversial Rezonings – Lazarus & Silvyn, P.C.) (New Rezoning Protest Law: Game-Changer for Controversial Rezonings – Lazarus & Silvyn, P.C.). (Arizona updated its statute in 2017 to make the 20% calculation encompass all sides of the rezoning parcel, making valid petitions harder to obtain (New Rezoning Protest Law: Game-Changer for Controversial Rezonings – Lazarus & Silvyn, P.C.).) Statutes: Ariz. Rev. Stat. §§ 9-462.04(H) (cities) and 11-814(D) (counties).
• Colorado: If owners of 20% of the land area within 150 feet of the subject property protest a zoning change, it can only be adopted by a two-thirds vote of all members of the local governing body (Memorandum). Statute: Colo. Rev. Stat. § 31-23-305 (municipal zoning). (Denver’s charter, reflecting state law, requires 10 of 13 council votes when a valid 20% protest is filed (Denver Referred Question 2N: The one about who has a say in rezoning …).)
• Connecticut: A protest petition by owners of 20% of the land affected by or within 500 feet of a proposed zone change forces a ? vote of the zoning commission or legislative body (depending on the jurisdiction) for adoption (Memorandum). Statute: Conn. Gen. Stat. § 8-3(b).
• Delaware: State law requires a ¾ vote of the municipality’s legislative body if 20% of property owners within 100 feet of the subject land protest a proposed zoning amendment (Memorandum) (Memorandum). Statute: Del. Code tit. 22, § 305.
• Illinois: A municipal zoning amendment facing a valid protest (written objection by owners of 20% of the subject property or adjacent frontage) cannot be adopted except by a two-thirds vote of the city council or board of trustees (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator) (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator). For county rezonings in Illinois, the protest threshold is similarly 20%, but the county board then needs a ¾ majority for approval (except in very small county boards, which may require ?) (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer) (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer). Illinois law even allows protests to text (not just map) amendments – if 5% of county landowners sign a protest to a text change, a ¾ vote is required (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer) (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer). Statutes: 65 ILCS 5/11-13-14 (municipal) and 55 ILCS 5/5-12014 (county).
• Iowa: A protest by owners of 20% of the land subject to rezoning or within 200 feet of it triggers a ¾ supermajority vote of the city council for approval ( Iowa Code Section 414.5 (2024) – Changes — protest. :: 2024 Iowa Code :: U.S. Codes and Statutes :: U.S. Law :: Justia). Counties in Iowa require at least a 60% vote when there is a valid 20% protest (Iowa Code § 335.7). Statutes: Iowa Code §§ 414.5 (cities) ( Iowa Code Section 414.5 (2024) – Changes — protest. :: 2024 Iowa Code :: U.S. Codes and Statutes :: U.S. Law :: Justia) and 335.7 (counties).
• Kansas: Under Kansas law (which follows the old Standard Zoning Enabling Act), if the owners of 20% or more of (a) the land proposed to be rezoned or (b) the land within the statutory notice area file a protest petition, the rezoning ordinance “shall not be passed except by at least a ¾ vote” of all members of the city or county governing body (2005-006 | 2/24/2005 | Kansas Attorney General Opinion). Statute: K.S.A. 12-757(f)(1).
• Massachusetts: Massachusetts uniquely requires a supermajority for all zoning amendments as a baseline rule. State law mandates that any adoption or change of a zoning ordinance or bylaw (map or text) must be approved by a two-thirds vote of the town meeting or city council ( Massachusetts General Laws Chapter 40a, Section 5 (2023) – Adoption or Change of Zoning Ordinances or By-Laws; Procedure :: 2023 Massachusetts General Laws :: U.S. Codes and Statutes :: U.S. Law :: Justia). (Recent reforms create limited exceptions: as of 2021, certain zoning changes that facilitate housing – such as ADUs or multifamily in “smart growth” districts – now can be adopted by a simple majority, but the general rule remains 2/3 for most zoning changes (General Law – Part I, Title VII, Chapter 40A, Section 5).) Statute: Mass. Gen. Laws ch.40A, § 5 ( Massachusetts General Laws Chapter 40a, Section 5 (2023) – Adoption or Change of Zoning Ordinances or By-Laws; Procedure :: 2023 Massachusetts General Laws :: U.S. Codes and Statutes :: U.S. Law :: Justia).
• Michigan: A protest petition against a city or village zoning amendment triggers a 2/3 vote requirement, unless a larger threshold (up to ¾) is set by local charter (MCL – Section 125.3403 – Michigan Legislature) (MCL – Section 125.3403 – Michigan Legislature). The petition must be signed by owners of at least 20% of the affected land or of land within 100 feet of it (MCL – Section 125.3403 – Michigan Legislature) (MCL – Section 125.3403 – Michigan Legislature). (Michigan’s law for county zoning differs: a valid protest delays the rezoning until after a referendum if demanded, rather than imposing a supermajority vote (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center).) Statute: Mich. Comp. Laws § 125.3403(1) (MCL – Section 125.3403 – Michigan Legislature) (MCL – Section 125.3403 – Michigan Legislature).
• Mississippi: If owners of 20% of the area in a proposed change or within 160 feet adjacent (including opposite lots) protest, the zoning amendment requires approval by three-fifths (3/5) of the governing body (Section 17-1-17 – Changes, Miss. Code § 17-1-17 | Casetext Search + Citator) (Section 17-1-17 – Changes, Miss. Code § 17-1-17 | Casetext Search + Citator). In other words, at least 60% of all members must vote in favor for the change to take effect. Statute: Miss. Code § 17-1-17 (Section 17-1-17 – Changes, Miss. Code § 17-1-17 | Casetext Search + Citator).
• Missouri: A protest by owners of 30% or more of the land area (subject site or within 185 feet) forces a proposed zoning change to need a two-thirds majority of the city council for passage (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator). (Missouri previously required ¾ approval with a 10% protest, but since 1988 the law was amended to the current 30%/? rule (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator).) Statute: Mo. Rev. Stat. § 89.060 (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator).
• Montana: A valid protest petition (owners of 20% of surrounding area or subject site) triggers a two-thirds vote requirement in Montana for municipal rezonings (Memorandum). Statute: Mont. Code § 76-2-305(2).
• Nebraska: Nebraska imposes different supermajority rules by jurisdiction: in cities, a protest by 20% of owners forces a ¾ vote of the city council, whereas in counties the same protest triggers a 2/3 vote of the county board (Memorandum) (Memorandum). Statutes: Neb. Rev. Stat. §§ 19-905 (city) and 23-165 (county).
• New Hampshire: In cities or towns that have a council vote on zoning changes, a protest petition by abutters (owners of 20% of the affected or nearby area) requires a two-thirds affirmative vote to adopt the change. In towns with Town Meeting, the protest petition causes the measure to need a 2/3 supermajority on the zoning ballot. Statute: N.H. Rev. Stat. § 675:5.
• New Jersey: A protest by owners of 20% of the area of the subject site or adjacent area triggers a requirement that a zoning amendment receive at least two-thirds of the full membership of the municipal governing body (Memorandum). Statute: N.J. Stat. § 40:55D-63.
• New Mexico: State law in New Mexico similarly provides that a ? vote of the elected commission or council is required for a zoning change if 20% of the owners of the affected area or within 100 feet file a protest. Statute: N.M. Stat. § 3-21-6(C).
• New York: Under New York’s zoning enabling acts, a ¾ supermajority vote is required if there is a protest by owners of at least 20% of (a) the land proposed for rezoning, or (b) the land immediately adjacent extending 100 feet, or (c) the land directly opposite (across the street) extending 100 feet from the street frontage of the opposite land (Third Department Decides Novel Question of Law Relating to Zone Change Protest Petitions Under Town Law § 265 | Long Island Land Use and Zoning). In such cases, the amendment “shall not become effective” unless approved by the heightened majority. Statutes: N.Y. Town Law § 265(1), Village Law § 7-708, General City Law § 83 (Third Department Decides Novel Question of Law Relating to Zone Change Protest Petitions Under Town Law § 265 | Long Island Land Use and Zoning) (Third Department Decides Novel Question of Law Relating to Zone Change Protest Petitions Under Town Law § 265 | Long Island Land Use and Zoning).
• North Dakota: A protest by 20% of nearby landowners triggers a ¾ vote requirement in North Dakota for city zoning changes. Statute: N.D. Cent. Code § 40-47-05.
• Oklahoma: Oklahoma’s protest provisions are unusually strict. For municipal rezonings, state law allows protests only if owners of 50% of the land within 300 feet object, in which case the city council must still muster a supermajority (e.g. 5 out of 7 members, ~71%) to approve () (). For county zoning, Oklahoma statutes go even further: in counties with >180,000 people, a valid protest forces a unanimous vote of the board for approval, whereas in counties over 500,000 population the requirement is somewhat relaxed to a simple majority of the board (Memorandum). Statutes: Okla. Stat. tit. 19, §§ 863.17, 868.16.
• South Dakota: A protest by 40% of landowners (or owners of 40% of land area – South Dakota’s threshold is notably higher than 20%) in a municipality triggers a ? vote requirement for a zoning change. Statute: S.D. Codified Laws § 11-4-5.¹
• Texas: Texas’s “valid petition” law requires a ¾ supermajority vote of the city council for any rezoning opposed in writing by owners of 20% of either (a) the land area subject to the change, or (b) the land within 200 feet of it (Texas Local Government Code – LOC GOV’T § 211.006 | FindLaw) (Texas Local Government Code – LOC GOV’T § 211.006 | FindLaw). In other words, if neighbors holding 20% of the adjacent land protest, a three-fourths vote is needed to enact the zoning change (Welcome to Texas, where majority doesn’t always rule) (Welcome to Texas, where majority doesn’t always rule). (For example, in a 7-member council, 6 votes would be required (Welcome to Texas, where majority doesn’t always rule).) Statute: Tex. Local Gov’t Code § 211.006(d) (Texas Local Government Code – LOC GOV’T § 211.006 | FindLaw).
• Wyoming: Wyoming law mandates a ¾ vote of the local governing body to approve a zoning change that has been formally protested by 20% of the owners of the subject or adjacent area. Statute: Wyo. Stat. § 15-1-603.

Note: In Ohio and West Virginia, state law provides an alternative mechanism: a qualified protest petition on a zoning amendment triggers a referendum of the voters rather than a supermajority council vote (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center). Likewise, Michigan’s county zoning law allows referenda on protested changes. These are exceptions to the supermajority approach.

Other Supermajority Requirements and Nuances

• Downzoning Protections: A few states impose supermajority rules in cases of downzoning (making zoning more restrictive) to protect property owners. For example, Wisconsin in 2018 prohibited general protest-petition requirements but mandated that any ordinance that downzones property (reducing its development rights) still requires a two-thirds vote of the local body (Zoning FAQ 5 | LWM, WI ) (Zoning FAQ 5 | LWM, WI ). This acts as a state-imposed supermajority requirement for certain zoning changes even without a neighbor petition.
• Distinction – Rezoning vs. Text Amendments: Protest petition statutes typically apply to map amendments (rezoning of specific property). Many states do not allow protests to trigger supermajorities for text amendments that apply citywide. For instance, New York’s and Texas’s statutes refer to changes in district boundaries or regulations affecting specific properties (Third Department Decides Novel Question of Law Relating to Zone Change Protest Petitions Under Town Law § 265 | Long Island Land Use and Zoning) (Texas Local Government Code – LOC GOV’T § 211.006 | FindLaw). However, a few states explicitly address text changes: Illinois, as noted, permits a county-wide 5% owner protest on text amendments (forcing a ¾ vote) (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer) (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer), and some states implicitly include any “amendment” unless exempted. Always check the statute’s language – some define “map amendment” vs. “text amendment” and set protest rules only for the former (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer) (Illinois Compiled Statutes 55 ILCS 5/5-12014 – Amendment of regulations and districts » LawServer). Generally, the supermajority-protest mechanism is aimed at rezonings where a discrete group of neighbors is uniquely affected.
• Local Charter Provisions: Home-rule cities can sometimes impose stricter voting rules, but state law may preempt them if they conflict. For example, Springfield, Missouri’s charter demanded a ¾ vote with only a 10% protest, but the Missouri Supreme Court struck it down as conflicting with the state’s 2/3-with-30% scheme in §89.060 (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator) (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator). The ruling confirmed that state law sets the minimum protest thresholds and required vote – cities cannot lower the protest percentage or raise the vote requirement in a way that frustrates the state scheme. In contrast, where state law gives latitude (e.g. Michigan allowing up to ¾ by local ordinance), local governments may choose to require a higher supermajority than the state minimum (MCL – Section 125.3403 – Michigan Legislature) (MCL – Section 125.3403 – Michigan Legislature).
• Comprehensive Plan Consistency: In some states, a rezoning inconsistent with the adopted comprehensive plan might necessitate a plan amendment or a higher vote, but most often the rule is an absolute one (cannot approve inconsistent rezoning absent a plan change) rather than a supermajority stipulation. For instance, Florida requires consistency with the comp plan by law, so an inconsistent rezoning would be illegal unless the plan is amended – there’s no separate supermajority vote rule, just a consistency mandate. Thus, while plan inconsistency alone typically doesn’t trigger a supermajority by statute, it effectively requires an extra legislative step (amending the plan, often itself needing supermajority or state approval). Always consult state planning statutes: the “consistency doctrine” can indirectly affect the process but is distinct from protest-petition supermajority provisions.

Summary: In sum, numerous states – including Texas, New York, Illinois, Arizona, Kansas, Iowa, Colorado, Connecticut, New Jersey, New Mexico, Delaware, Mississippi, Missouri, Montana, Nebraska, the Dakotas, Wyoming, and others – have laws empowering neighbors to force a higher voting threshold on rezonings (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center) (Memorandum). These laws generally require a two-thirds or three-fourths majority for approval when a defined percentage of nearby owners object in writing, with a few states charting their own course (Massachusetts’ across-the-board 2/3 requirement, Wisconsin’s downzoning rule, North Carolina’s repeal of protest petitions in 2015, etc. (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center) (Zoning FAQ 5 | LWM, WI )). The exact triggers and fractions vary by state, so the specific statutory language and any recent amendments or case law should be reviewed in each jurisdiction. The citations above to state codes and cases provide the legal basis for these supermajority zoning requirements.

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¹ South Dakota’s statute uses 40%; see S.D. Codified Laws § 11-4-5 (municipal protest petitions) and § 11-2-19 (for county zoning, 20% triggers 2/3 vote).

Sources:

• State zoning enabling statutes (see Appendix of state citations (Memorandum) (Memorandum); e.g., Tex. Local Gov’t Code § 211.006(d) (Texas Local Government Code – LOC GOV’T § 211.006 | FindLaw); N.Y. Town Law § 265(1) (Third Department Decides Novel Question of Law Relating to Zone Change Protest Petitions Under Town Law § 265 | Long Island Land Use and Zoning); Kan. Stat. § 12-757 (2005-006 | 2/24/2005 | Kansas Attorney General Opinion); Ill. Municipal Code 65 ILCS 5/11-13-14 (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator); Miss. Code § 17-1-17 (Section 17-1-17 – Changes, Miss. Code § 17-1-17 | Casetext Search + Citator); Mo. Rev. Stat. § 89.060 (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator); Mass. G.L. c.40A § 5 ( Massachusetts General Laws Chapter 40a, Section 5 (2023) – Adoption or Change of Zoning Ordinances or By-Laws; Procedure :: 2023 Massachusetts General Laws :: U.S. Codes and Statutes :: U.S. Law :: Justia); etc.).
• Policy analysis and summaries: e.g., Mercatus Center report on protest petitions (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center) (Rezoning Protest Petitions Are Ripe for Reform | Mercatus Center); Wyoming LSO legal memo summarizing 22 state protest statutes (Memorandum) (Memorandum).
• Case law: City of Springfield v. Goff, 918 S.W.2d 786 (Mo. 1996) (state vs. local supermajority rules) (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator) (City of Springfield v. Goff, 918 S.W.2d 786 | Casetext Search + Citator); Matter of Eadie v. Town Bd. of N. Greenbush, 7 N.Y.3d 306 (2006) (discussing NY protest provisions); see also N.C. Session Law 2015-160 (repealing N.C. Gen. Stat. 160A-385 regarding supermajority) (The Zoning Protest Petition is No More: Super-Majority Provision Repealed – Coates’ Canons NC Local Government Law) (The Zoning Protest Petition is No More: Super-Majority Provision Repealed – Coates’ Canons NC Local Government Law).

Salim’s conclusion

Human writing again. This output is about equal in quality to a policy brief of mine; it’s certainly on par with what I would expect from a research assistant. Even with the crutch provided by my published list, it wasn’t fooled and found two laws that I had missed. And it’s vastly more accurate than the other research I saw on this topic, which was performed by an intern at a trade organization, was terribly inaccurate, and was widely distributed to state legislators.