There is no single statute called the California Clean Air Act. When people use that phrase, they are usually referring to the bundle of California laws that regulate air pollution, anchored by the 1967 Mulford-Carrell Air Resources Act and expanded by greenhouse gas laws like AB 32 and SB 32. Together, these laws give California the most aggressive air quality system in the country, run by the California Air Resources Board (CARB) and backed by a unique federal waiver that lets the state set vehicle emission standards stricter than the federal government’s.
The Core Laws and Who Enforces Them
California’s centralized air quality agency traces back to 1967, when Governor Ronald Reagan signed the Mulford-Carrell Air Resources Act. That law merged the Bureau of Air Sanitation and the California Motor Vehicle Pollution Control Board into CARB.1California Air Resources Board. History Health and Safety Code Section 39000 declares that Californians have a primary interest in the quality of their physical environment and that atmospheric pollution threatens public health and safety.
CARB’s operational authority comes from Health and Safety Code Section 39600, which directs the board to take whatever actions are necessary to carry out its powers under state law.2California Legislative Information. California Code Health and Safety Code 39600 – General Powers and Duties Section 39601 authorizes CARB to adopt standards, rules, and regulations through formal rulemaking.3Justia. California Health and Safety Code 39600-39619.6 – General Powers and Duties In practice, CARB sets statewide emission limits, runs testing programs, and enforces penalties.
CARB doesn’t do it alone. Under Health and Safety Code Section 39002, local and regional air quality management districts have primary responsibility for controlling pollution from non-vehicle sources like factories, refineries, and construction sites. CARB handles vehicle emissions statewide, while roughly three dozen regional districts cover stationary sources within their boundaries. If a regional district fails to meet its obligations, CARB can step in and take over enforcement.
The Federal Waiver That Makes California Different
Federal law normally bars states from setting their own emission standards for new vehicles. California is the sole exception. Under Section 209 of the federal Clean Air Act (42 U.S.C. § 7543), the EPA must grant a preemption waiver to any state that regulated vehicle emissions before March 30, 1966, a requirement only California meets, as long as the state’s standards are at least as protective as federal ones.4Office of the Law Revision Counsel. 42 US Code 7543 – State Standards The EPA can deny the waiver only if it finds California’s determination arbitrary, the state doesn’t face compelling and extraordinary conditions justifying separate standards, or the standards conflict with federal vehicle-performance requirements.
Once California receives a waiver, other states can adopt California’s standards wholesale under Section 177 of the Clean Air Act (42 U.S.C. § 7507). A state must adopt standards identical to California’s and do so at least two model years before the standards take effect.5Office of the Law Revision Counsel. 42 USC 7507 – New Motor Vehicle Emission Standards in Nonattainment Areas More than a dozen states have exercised this option, which means California’s vehicle rules effectively set the standard for a significant share of the national new-vehicle market.
The waiver process is politically charged. Administrations have granted, revoked, and reinstated California’s waivers multiple times. As of early January 2025, the EPA issued notices of decision on several California waiver requests, including the Advanced Clean Cars II regulations, and California withdrew certain other requests.6US EPA. Vehicle Emissions California Waivers and Authorizations The status of any particular waiver can change with a new administration, so check the EPA’s waiver page for the current picture.
What the Vehicle Rules Require
Standards Manufacturers Must Meet
Every new car or light truck sold in California must meet the Low Emission Vehicle standards in Title 13 of the California Code of Regulations.7California Air Resources Board. Light-duty Vehicle Regulations and Test Procedures LEV III rules covered model years 2015 through 2025. Starting with the 2026 model year, LEV IV takes over with stricter exhaust limits.
Layered on top of LEV is the Zero-Emission Vehicle mandate, now governed by the Advanced Clean Cars II regulations adopted in 2022. This rule requires that 100 percent of new passenger vehicles sold in California meet zero-emission standards by the 2035 model year.8California Air Resources Board. Advanced Clean Cars The transition ramps up on a fixed schedule:9California Air Resources Board. Section 1962.4 ZEV Standards 2026 and Subsequent Model Years
- 2026: 35%
- 2027: 43%
- 2028: 51%
- 2029: 59%
- 2030: 68%
- 2031: 76%
- 2032: 82%
- 2033: 88%
- 2034: 94%
- 2035 and after: 100%
Plug-in hybrid electric vehicles count toward an automaker’s ZEV requirement, but they can satisfy no more than 20 percent of the overall obligation.10California Air Resources Board. California Moves to Accelerate to 100% New Zero-Emission Vehicle Sales by 2035 Battery-electric and hydrogen fuel cell vehicles carry full credit. Manufacturers that fall short must buy credits from competitors that exceeded the target or face penalties.
What Drivers Have to Do: Smog Check
For individual vehicle owners, the compliance obligation runs through California’s Smog Check program. Health and Safety Code Section 44000 directs the state to maintain a vehicle inspection and maintenance network that meets or exceeds federal clean air standards.11California Legislative Information. California Health and Safety Code 44000 Most gasoline, hybrid, and alternative-fuel vehicles must pass a Smog Check inspection to renew their registration.
Not every vehicle needs an inspection every cycle. Vehicles eight model years old or newer are exempt from the biennial Smog Check requirement for registration renewal. For change-of-ownership transactions, the exemption window is shorter, covering only vehicles four model years old or newer. Diesel vehicles have no model-year exemption at all.12Bureau of Automotive Repair. Smog Check: When You Need One and Whats Required A Smog Check is also required when a vehicle is first registered in the state, regardless of age or fuel type.
Inspections must be performed at stations licensed by the Bureau of Automotive Repair. The state does not regulate the labor cost of the inspection itself, but every station charges an $8.25 state certificate fee.12Bureau of Automotive Repair. Smog Check: When You Need One and Whats Required Total out-of-pocket costs vary by station and location.
If a vehicle fails, the owner must complete emissions-related repairs and pass a retest before the DMV will renew registration. Some owners who meet income requirements may qualify for the state’s Consumer Assistance Program, which helps cover repair costs. Driving with expired registration because of a failed smog test triggers DMV late-registration penalties. Those penalties are percentage-based: the state adds a percentage of the vehicle license fee, starting at 10 percent for 1–10 days late and climbing to 160 percent after two years, plus flat registration and CHP late fees that grow at each tier.13California Department of Motor Vehicles. Penalties Resolving a failed smog test promptly usually costs far less than waiting.
Greenhouse Gas Targets and Cap-and-Trade
California’s greenhouse gas strategy is built on a series of escalating reduction targets. AB 32, the Global Warming Solutions Act of 2006, required the state to cut emissions to 1990 levels by 2020.14California Air Resources Board. AB 32 Global Warming Solutions Act of 2006 SB 32, signed in 2016, raised the bar to at least 40 percent below 1990 levels by 2030.15California Legislative Information. SB 32 Senate Bill – Chaptered More recent legislation (AB 1279) targets carbon neutrality by 2045.
The main enforcement tool for these targets is the cap-and-trade program. Launched in 2013, it places a declining annual cap on total greenhouse gas emissions from major sources. Companies that emit below their allowance can sell surplus credits; those that exceed it must buy additional allowances at quarterly auctions.14California Air Resources Board. AB 32 Global Warming Solutions Act of 2006 Auction revenue flows into the Greenhouse Gas Reduction Fund, which finances transit projects, affordable housing near transit, and other emission-reduction programs.
Penalties for Violations
Violating California’s air quality laws carries real consequences. Under Health and Safety Code Section 42400, a general violation of any CARB or air district rule, regulation, permit, or order is a misdemeanor punishable by a fine of up to $5,000 or up to six months in county jail, or both.16California Legislative Information. California Health and Safety Code 42400 If the violation causes actual physical injury to a considerable number of people, the maximum fine rises to $15,000 and the potential jail time increases to nine months. Each day a violation continues counts as a separate offense, so penalties can compound quickly.
These criminal penalties sit alongside civil enforcement tools. CARB and regional air districts can issue administrative citations, seek injunctions, and impose per-day civil penalties for stationary-source violations. For vehicle manufacturers, falling short of ZEV mandate percentages means buying credits or facing per-vehicle fines. Whether you’re running a refinery, selling cars, or renewing your registration, California’s air quality framework has a mechanism aimed at your part of the system.