Air Quality Modeling Given the Trump Administration’s Clean Air Act Actions

The Regulatory Backdrop

Air quality modeling often requires assumptions about future motor vehicle emissions standards. However, these assumptions have been complicated by (1) the 2025 revocation of California’s Clean Air Act waivers, which previously allowed California to adopt motor vehicle emissions regulations on its own, and (2) the 2026 federal rescission of the GHG endangerment finding under the Clean Air Act. More specifically, in May 2025, the U.S. Senate approved several bills under the Congressional Review Act which purported to rescind California’s Clean Air Act waivers. (H.J.Res. 87, H.J.Res. 88, H.J.Res. 89.) The U.S. Senate Parliamentarian and the Government Accountability Office both concluded that the bills were illegal. California and other states also filed a lawsuit challenging the waiver revocations. (See State of California et al v. U.S.A. et al. (2025) N.D. Cal Case No. 25-CV-04966.) Furthermore, the 2026 administration rescinded the GHG endangerment finding and removed federal GHG motor vehicle emissions standards from 40 CFR part 600. (Vol. 90 Federal Register, No. 146, 36288.) This decision has been challenged in American Public Health Association, et al. v. United States Environmental Protection Agency and Lee Zeldin, Administrator, Case No. 26-1037 (D.C. Cir., filed Feb. 18, 2026). Consequently, there is substantial legal uncertainty about future motor vehicle emissions standards. Given this uncertainty, public agencies should be able to “make reasonable assumptions based on substantial evidence about future conditions without guaranteeing that those assumptions will remain true.” (Cal. Pub. Resources Code, §21080(e); City of Del Mar v. City of San Diego (1982) 133 Cal.App.3d 401, 412.)

CARB’s Response

In response to this regulatory uncertainty, in January 2026 the California Air Resources Board (CARB) revised the emissions factors for air quality modeling programs and released revised greenhouse gas (GHG) adjustment factors for EMFAC2021 to remove the estimated emissions benefits underlying ACT, Zero-Emission Airport Shuttle, Omnibus and Warranty Phase I regulations. These adjustment factors were developed for the EMFAC2021 model rather than the more recent EMFAC2025 model version as the use of EMFAC2025 might result in underestimating future emissions if the rescission remains, depending in part upon the outcome of these cases.

Related Case Law

Similar modeling issues have arisen in other CEQA cases, which may provide useful guidance in navigating this uncertainty:

  • Planning and Conservation League v. Castaic Lake Water Agency (2009) 180 Cal.App.4th 210, 249
  • Bay Area Citizens v. Association of Bay Area Governments (2016) 248 Cal.App.4th 966, 1017.)

 

 

CEQA Water Supply Analyses: Court Clarifies Disclosure Requirements

Vallejo v. City of American Canyon (2026) 117 Cal.App.5th 1112

This case is a helpful guide for practitioners involved in the preparation of water supply analyses and the disclosure of water supply uncertainty.

The Court’s Analysis

Petitioner first asserted the WSA was inadequate for failing “to disclose amount of water actually purchased—as opposed to the amount of water available for purchase.” In rejecting this assertion, the Court reasoned the City has “historically received ‘100 percent of the full contracted volume’ of…permit water for all but one year.”

Petitioner next asserted the WSA failed to disclose “place of use restrictions” which it alleged violated CEQA’s requirements to discuss the uncertainty of the project’s water supply. The Court reasoned that this restriction did not fall within the restrictions identified under CEQA Guidelines Section 15155(f)(3) (i.e. “drought, salt-water intrusion, regulatory or contractual curtailments.”) The Court also reasoned “the place of use restrictions do not reduce the overall volume of water; they merely limit the areas within American Canyon that can receive that water.”

Finally, Petitioner alleged the WSA was inadequate for failing to address monthly curtailment during drought conditions in lieu of an annual analysis and “simultaneous curtailment” from the City’s different water providers. The Court rejected the first argument, explaining that nothing under CEQA or the water code mandated monthly analyses and that courts “cannot interpret the regulation to impose procedural or substantive requirements beyond those explicitly stated,” consistent with Pub. Res. Code §21083.1. The Court found the second argument meritless because the “EIR also discusses the possibility that water from either source might be curtailed, and supply reductions in Vallejo could lead to proportionate reductions.”

The Broader Trend

We’re seeing similar arguments being rejected by other courts, including one of the firm’s recent superior court wins defending the City of Seaside’s General Plan update and water supply analysis in Center for Biological Diversity v. City of Seaside (2025, Monterey Superior Court Case No. 24CV002483 [Rejecting the argument that General Plan EIR’s water supply analysis failed to discuss CBD’s Settlement Agreement with the Water Supplier which purported to limit “groundwater-sourced water supply” in the absence of developing new water supplies.])

The Bottom Line

These decisions confirm that agencies have meaningful flexibility in how they analyze water supply reliability under CEQA, so long as their conclusions are grounded in historical delivery data and a reasoned discussion of curtailment risk.

Appellate Decision Clarifies Scope of Programmatic EIR Analysis for Housing Element Sites

The Committee for Tiburon LLC v. Town of Tiburon (2026) 118 Cal.App.5th 259.

Why This Matters

This appellate decision may be one of the most interesting cases from 2026 for individuals preparing programmatic EIRs. The question presented to the Court was “if a local government is updating its general plan and housing element site inventory and no specific housing project has been proposed for a listed site, must the EIR for the general plan analyze site-specific environmental impacts of potential development of the site.” The Court concluded that no such analysis was required.

Background

The Town’s General Plan update included 17 potential sites that would accommodate the regional housing needs allocation. However, identification of these 17 sites did not mean development on any particular site was reasonably foreseeable. Housing Elements are generally required to provide “more residential units than the minimum number of units required by the RHNA to allow for a buffer.” After receiving comments on the suitability of Site H for Housing, the Town prepared additional studies of Site H’s constraints and traffic to demonstrate that it was suitable for redevelopment.

The Court’s Ruling

Petitioner sought to preserve Site H, a largely vacant nine acre parcel, which would be allowed to build up to 118 units under the updated plan. Petitioner asserted that site specific analysis of Site H should have occurred because (1) the additional Site H studies made site specific review feasible, and (2) “if no site-specific environmental review for Site H is included in this EIR, then such analysis will never be included [due to potential use of statutory housing exemptions].” The Court rejected both arguments, first reasoning that “without a proposed project that identifies critical factors such as the amount and configuration of the proposed housing…the Town can only speculate as to the severity of any particular environmental impact.” Secondly, the Court reasoned that “the possibility that a future housing project may qualify for a CEQA exemption does not, by itself, make site-specific impacts more feasible to analyze at the general plan and housing element stage.”

The Broader Trend

This second argument appears to be arising more often in CEQA litigation involving long range plans. This might be attributable to increased statewide policies which are making more developments ministerial and exempt from CEQA. For example, in Sacramentans for Fair Planning v. City of Sacramento (2019) 37 Cal.App.5th 698 Petitioner faulted the city’s environmental analysis, alleging that the programmatic analysis did not identify “residential densities and building intensities within the region to the extent necessary to enable a project’s significant effects to be mitigated, and thus it cannot form the basis for justifying streamlined CEQA review.” The Court rejected this assertion, reasoning “Plaintiff’s concern that some type of environmental review may not occur by using an SCEA in this instance is a complaint to take to the Legislature…If it chose to exempt certain types of development from full environmental review based on those rational bases, we are not at liberty to question their wisdom.”

However, such exemptions are not strictly limited to those adopted by the legislature. Similar issues also arose in San Diego Citizenry Group v. County of San Diego (2013) 219 Cal.App.4th 1, where the County adopted “regulatory amendments streamlining the winery approval process and allowing small boutique wineries ‘by right.’” Petitioner alleged the county violated CEQA by eliminating its discretionary process “which allowed by-right use without further discretionary review,” “[Petitioner] claims this is a ‘uniquely problematic’ case because boutique wineries will be allowed by right and thus without further mitigation.” In rejecting such assertions, the Court reasoned “CEQA does not, indeed cannot, guarantee that [an agency’s] decisions will always be those which favor environmental considerations,” and upheld the agency’s policy decision “given the Project objectives of encouraging the growth of agriculture and the wine industry by streamlining.”

The Bottom Line

Practitioners preparing programmatic EIRs for general plans and housing elements should take note: courts continue to reject arguments that plan-level review must analyze site-specific impacts merely because more detailed studies could theoretically be developed, or because future ministerial approvals might otherwise escape CEQA review altogether.

Three Lawsuits, Fifteen Years, One Project: Court Draws the Line on Successive CEQA Challenges

Bair v. California Department of Transportation (2026) 119 Cal.App.5th 579

Why This Matters

This decision offers important guidance on how claim preclusion doctrines apply to successive CEQA challenges arising from the same project, and reflects the courts’ growing impatience with serial litigation strategies.

Background

Bair is the third lawsuit over the last 15 years which challenged a highway project through an old-growth redwood grove which would reconfigure an existing 1 mile stretch in Humboldt County. This litigation may be familiar to some readers, as the prior published appellate decision faulted Caltrans’ EIR for failing to disclose the project’s pre-mitigation impact conclusions regarding the redwood trees and relying upon a non-regulatory handbook to conclude impacts were less than significant. (Lotus v. Department of Transportation (2014) 223 Cal.App.4th 645.) The second lawsuit involved a successful procedural challenge to an Addendum which attempted to fix the substantive deficiencies in the prior EIR. However, this second lawsuit did not address the substantive analysis in the Addendum. In response to these losses, Caltrans circulated the previous EIR and pre-existing Addendum for public review unchanged, and reapproved the project in 2023. Caltrans then sought discharge of the writ from the prior case.

The Court’s Ruling

This third case at issue in Bair involved a simultaneous challenge on the discharge of the writ from the prior case and a new independent lawsuit. Petitioner faulted Caltrans’ substantive analysis of biological impacts to the old-growth redwood trees. The Court of Appeal ruled that Petitioner’s third lawsuit was barred by res judicata/claim preclusion, which bars litigation not only of issues that were actually raised in the prior case, but those that could have been raised, but were not. In assessing the preclusive effect of the prior litigation, the court noted that the central question was “whether the revised EIR’s compliance with CEQA could have been adjudicated in response to the [agency’s] post judgment request to discharge the writ.” The Court reasoned that Petitioner could have appealed the ruling in the original Lotus case if they believed that the court erred, but they did not do so. In clarifying the standard for applicability of claim preclusion, the Court of Appeal disagreed with the reasoning in Central Delta Water Agency v. Department of Water Resources (2021) 69 Cal.App.5th 170.

The Bigger Picture

In a growing trend among CEQA cases, the Court lamented that CEQA is more often being used as “a never-ending battle…that can drag on for years, even decades.” Similar concerns were raised in Tiburon Open Space Committee v. County of Marin (2022) 78 Cal.App.5th 700, 781-783; Citizens of Goleta Valley v. Board of Supervisors (1990) 52 Cal.3d 553, 576 [“we caution that rules regulating the protection of the environment must not be subverted into an instrument for the oppression and delay of social, economic or recreational development and advancement.”]; County of Orange v. Superior Court (2003) 113 Cal.App.4th 1, 6 [“[t]he Legislature has obviously structured the legal process for a CEQA challenge to be speedy, so as to prevent it from degenerating into a guerilla war of attrition by which project opponents wear out project proponents.”].  While this might not be a legal basis for seeking dismissal of a CEQA case, practitioners may wish to incorporate similar themes into their briefing.

What to Watch

Readers should be aware that a request to de-publish this opinion was filed on May 26, 2026, which had not been addressed yet by the Supreme Court as of July 14, 2026.

California Supreme Court Clarifies “Negligible Expansion” Under the Class 1 CEQA Exemption

Sunflower Alliance v. California Department of Conservation (Case No. S287414.)

Why This Matters

After two years without weighing in on a CEQA case, the California Supreme Court has issued a significant decision clarifying the scope of CEQA’s Class 1 categorical exemption for minor alterations to existing facilities. For practitioners and agencies who rely on this commonly used exemption, the Court’s new standard for what counts as a “negligible expansion” of use is required reading, and its remand leaves an important secondary issue about permissible mitigation conditions still very much alive.

The Decision

On June 25, 2026, the Court issued its decision in Sunflower Alliance v. California Department of Conservation (Case No. S287414). The Supreme Court clarified what constitutes a “negligible expansion” of an existing or former use under CEQA’s Class 1 categorical exemption for minor alterations of existing facilities. (CEQA Guidelines §15301.) Notably, this was not the issue the Supreme Court initially accepted for review. The initial question was whether an agency may claim a categorical exemption while also adopting project conditions, pursuant to regulatory mandates, related to potential environmental effects.

Background

This case involved the agency’s use of this Class 1 exemption for the conversion of a dormant oil and gas extraction well, plugged in 1984. This well would be converted and used to re-inject treated wastewater, a byproduct of such drilling from other sites. Petitioners argued the use of the Class I exemption was improper as it did not meet the definition of a “negligible expansion.”

The Court of Appeal disagreed, concluding the “negligible expansion” should focus on whether “the proposed expansion would pose only a negligible additional risk of environmental harm.” The Appellate Court reasoned “no purpose is served by myopically focusing on whether a use is new, thereby excluding from the exemption many projects that would cause no environmental harm, precisely the type of borderline projects for which categorical exemptions are useful.” In the Supreme Court, Petitioner sought reversal, arguing that “negligible expansion” “excludes new uses from the scope of the class 1 exemption.”

The Supreme Court’s Ruling

The Supreme Court did not accept either Petitioner’s or Respondent’s definition of “negligible expansion,” instead concluding the California Natural Resources Agency (CNRA), which promulgates the CEQA Guidelines, was “closest to the mark.” The Supreme Court concluded that “an agency should examine the nature and scope of the proposed expansion of use, rather than its potential environmental effects, in making its exemption determination.” In doing so, the Supreme Court rejected Petitioner’s interpretation, that “‘expansion’ excludes new uses from the scope of the class 1 exemption.” The Supreme Court did not reach a final conclusion on the applicability of the Class 1 exemption to the project, instead remanding the case back to the Court of Appeal for reconsideration in light of this new definition.

What to Watch on Remand

On remand, it will be interesting to see whether Respondents pivot to any alternative CEQA exemptions, such as the common-sense exemption (CEQA Guidelines §15061(b)(3)), which allows for consideration of the scope of the project’s environmental impacts.

If so, this may reinvigorate the issue the Supreme Court initially accepted for review: i.e. What constitutes impermissible CEQA mitigation in a categorical exemption?

This issue continues to arise in numerous CEQA cases:

  • Salmon Protection & Watershed Network v. County of Marin (2004) 125 Cal.App.4th 1098, 1102 [conditions constituted impermissible mitigation.]
  • Wollmer v. City of Berkeley (2011) 193 Cal.App.4th 1329, 1353 [voluntary dedication by developer of land for turn lane to alleviate existing traffic conditions, not an improper mitigation measure.]
  • Save the Plastic Bag Coalition v. City & County of San Francisco (2014) 222 Cal.App.4th 863 [bag fee was not an unlawful mitigation measure.]
  • San Francisco Beautiful v. City and County of San Francisco (2014) 226 Cal.App.4th 1012 [“An agency may rely on generally applicable regulations to conclude an environmental impact will not be significant and therefore does not require mitigation.”]
  • Citizens for Environmental Responsibility v. State ex rel.14th Dist. Ag. Assn. (2015) 242 Cal.App.4th 555, 574 [Manure Management Plan was not an impermissible mitigation measure.]

The Bottom Line

Agencies and project applicants relying on the Class 1 exemption should revisit their exemption analyses to ensure they focus on the nature and scope of a proposed expansion, not merely its potential environmental effects, and should watch for further developments on remand, which could reshape how mitigation conditions interact with categorical exemptions more broadly.

Have questions? Contact us.

Failure to Comply with Claims Presentation Requirement Cannot be Cured After Lawsuit is Served on a Public Entity

In a published opinion issued on June 2, 2026, the Second Appellate District affirmed the importance of the Government Claims Act’s claim presentation requirement. The Court held that a plaintiff’s failure to present the claim to the public entity before filing and serving a lawsuit was a fatal defect that could not be cured.

Harland v. City of West HollywoodB343375, involved a slip and fall plaintiff who mailed a government claim to the City and, just two days later, filed a lawsuit against the City. Fifteen days after the City received the claim, and before the City denied the claim, the plaintiff served the lawsuit on the City. Recognizing that the suit was filed prematurely, the plaintiff tried to cure the defect after the claim had been denied by first amending the complaint, and then dismissing the complaint to re-file as a new case.

The Court of Appeal held that the plaintiff’s failure to comply with the claims presentation requirement before initially filing and serving the complaint on the City was fatal to her claim, and could not be cured. Not only did the Court lay out a bright line rule, but it provided powerful language on the purpose and importance of the claims presentation requirement: claim presentation “ensures public entities get sufficient information to investigate claims without the expense of litigation” and that function is defeated when a plaintiff prematurely files suit. Harland reinforces the importance of public entities weighing any claim presentation defense as part of an initial litigation evaluation. As the Court succinctly put it, “[t]ime spent on litigation is gone forever and can never be recovered.”

As litigation costs continue to rise, Harland gives public entities and their counsel a clear mandate — evaluate claim presentation compliance at the outset of every tort matter, because it can be the difference between quick resolution and protracted litigation.

Neighbor Disputes in High-Value Commercial and Residential Real Estate

Whether your neighbors are adjacent businesses in a commercial complex, or the family who lives on the other side of the wall in your backyard, neighbor disputes can easily turn into the most stressful and cumbersome aspect of one’s life. Getting early guidance from an experienced attorney familiar with land use and real estate disputes may avoid some of the worst outcomes.

For those with investments in high-end residential, commercial, industrial, or mixed-use property, conflicts with adjacent owners can stall projects, impair value, and divert attention from the original goals. What begins as a simple boundary issue, construction problem, or access concern can quickly escalate into regulatory complaints, nuisance claims, or even litigation.

Land-Use and Real Property Disputes Have Commonalities

In California, disputes surrounding real property and land-use tend to cluster around a few recurring issues:

  • Nuisance allegations: Noise, traffic, lighting, construction impacts, or disruptive business operations.
  • Easements, CC&Rs, and recorded restrictions: Often overlooked limitations that constrain use, expansion, or operations.
  • Encroachments: Walls, fences, retaining structures, or unpermitted improvements tied to assumed property lines.
  • Trees and landscaping: Damage claims, view disputes, and statutory exposure.
  • Access issues: Shared driveways, ingress and egress, or modified easements.
  • New development opposition: Neighbor challenges aimed at delay or leverage.

Why Early Positioning Matters

Often, it is the first pitch that sets the stage for the entire game. An initial combative meeting or aggressive letter from counsel can derail any hope for amicable resolution of these issues, as such encounters can lead to emotions overtaking any subsequent rational positioning and decision making. Attorneys are often brought into the picture too late – when the situation has gotten so bad that there is no other choice. However, it is early legal positioning that limits legal/financial exposure and preserves optionality.

Disputes escalate fastest when assumptions replace thorough analysis, or when early responses are handled informally without a clear litigation strategy in mind. For example, an attorney can provide an early objective analysis of the legal issues, and what each party is likely to achieve if the dispute ends up in litigation. Having this analysis in hand (including potentially including third party experts such as surveyors, contractors, or experts) before dealing with the other side will inform the strategy for those initial negotiations.

When Disputes Escalate

Not every dispute can be resolved informally. Some are emotional. Others are strategic and tied to timelines, regulatory requirements, or enforceable restrictions. In either case, disciplined communication and a defensible strategy help preserve credibility, leverage, and long-term value.

Commercial and residential neighbor disputes are common, but they are manageable. A thoughtful early approach can limit disruption, preserve leverage, and keep objectives in focus.

Proposed New Federal Rule Regarding AI-Generated Evidence

Evidence generated by artificial intelligence (“AI”) is making its way into courtrooms. As a result, the U.S. Judicial Conference’s Advisory Committee has proposed a new rule “to regulate the admissibility of machine evidence that is introduced without the testimony of any expert.” The proposed rule marks an important effort to address concerns raised by the use of AI in courts of law and has generated extensive discussion and comments from judges, lawyers, and other interested parties across the country.

As proposed by the Advisory Committee, Federal Rule of Evidence 707 (“Proposed Rule 707”) would subject “machine-generated evidence” to the same admissibility standard as expert testimony. The proposed rule reads:

When machine-generated evidence is offered without an expert witness and would be subject to Rule 702 if testified to by a witness, the court may admit the evidence only if it satisfies the requirements of Rule 702 (a)-(d). This rule does not apply to the output of simple scientific instruments.

The Advisory Committee released Proposed Rule 707 for public comment in August 2025, and the public comment period closed this week on February 16, 2026.

Select issues raised by commenters in response to Proposed Rule 707 include:

  • The phrase “machine-generated evidence” is undefined. While the Committee Notes illustrate that this rule is intended to address AI-generated evidence, the absence of a definition of those terms creates vagueness and ambiguity, and the scope of evidence targeted by the rule is unclear.
  • The procedure for admitting machine-generated evidence using Rule 702 standards is uncertain because there might not be a qualified expert to examine regarding the proffered evidence. Thus, evidence offered under Proposed Rule 707 could spur more disputes and higher litigation costs than traditional expert testimony.
  • Proposed Rule 707 may be premature at this time. AI technology and the public’s understanding of such technology continues to evolve rapidly, and it is unclear whether this rule creates the flexible framework needed to provide guardrails for such technology efficiently.

Notably, Proposed Rule 707 only attempts to address concerns with admissibility of evidence a party acknowledges to be AI-generated, and does not begin to address problems with unacknowledged AI-generated evidence, like deepfakes. Amendments and additions to Federal Rule of Evidence 901 have been suggested to deal with such authentication issues, but the scheme the Advisory Committee will choose to deal with the myriad problems generated by AI in the courtroom remains to be seen.

The Advisory Committee will review and process the public comments on Proposed Rule 707 and provide a final report on the matter in June 2026.

Workplace Know Your Rights Act (SB 294) Addresses Immigration & Workers Comp Concerns

California employers face new compliance requirements in 2026, including written employee notices and emergency-contact procedures tied to significant fines.

By February 1, 2026, employers must provide a written notice to each employee of certain workplace rights, including, among other things, workers compensation and notice requirements related to inspections conducted by immigration authorities. The Labor Commissioner has posted a template notice on its website that employers can use to be compliant.

Employers are required to provide the notice to employees upon hire and annually. An employer’s failure to comply will lead to a $500 fine per employee, per violation.

Additionally, on or before March 30, 2026, employers must provide employees an opportunity to designate an emergency contact. The employer must inform the emergency contact if the employee is arrested or detained on site. Failure to comply will lead to a fine of $500 per employee, per day the violation occurs, up to a maximum of $10,000 per employee.

Early review and updates to onboarding and notice practices can help avoid costly penalties in 2026. If you have questions or need assistance, contact us.

For a summary of all new labor and employment laws California employers should know, download a copy of our new 2026 Employment Law Legal Update.

WOTUS Overhaul: Clean Water, New Rules

The EPA and the US Army Corps released a proposed new definition of “Waters of the United States” (WOTUS) on November 17, 2025, marking yet another major shift in how federal jurisdiction is asserted under the Clean Water Act. Once a strict framework for protecting wetlands and streams, the proposed definition now aims to balance water protection with accelerated growth and economic opportunity. This change responds directly to the Supreme Court’s Sackett v EPA decision.

Key takeaways from the proposed definition:

Revisions to key definitions:

  • “Relatively permanent waters”: only includes bodies of surface water that are standing and continuously flowing “year-round or at least during the wet season”, e.g., lakes or rivers
  • “Continuous surface connection” for wetlands: wetlands must physically touch a regulated water body to qualify
  • “Tributaries”: must connect to navigable water body, directly or through other connected features

New and clarified exclusions proposed:

  • Intrastate lakes or ponds or interstate waters unless otherwise jurisdictional (per above)
  • Groundwater
  • Waste treatment systems
  • “Prior converted” farmland and certain ditches

Why this matters: 

  • Landowners, agriculture, and businesses: Greater predictability and fewer permitting hurdles
  • States and Tribes: Enhanced authority to shape local water regulations
  • Environmental Advocates: Concern that protections—especially for wetlands lacking clear connections—are weakened

Next steps: 

The proposed new definition is now open for public comment, and the EPA will hold public meetings to gather input. For support in reviewing the proposal or preparing and submitting a comment, please contact Meyers Nave. Stay tuned for how this rule ultimately lands.