In a series of tweets Wednesday morning, President Trump said that his administration “is revoking California’s Federal Waiver on emissions”—a reference to the waiver of preemption under the federal Clean Air Act granted California by the US Environmental Protection Agency (EPA) in the Obama Administration in 2012.

However, the revocation—if it is legally possible, of which there is some question—reprises a conflict between California and the Bush Administration, which denied California a waiver in 2007 requested to regulate automotive greenhouse gas emissions (earlier post).

At the time, California vowed it would sue to resolve the issue. However, the subsequent election of Barack Obama as president intervened, and the EPA under the new administration issued California the waiver it sought, as well as a subsequent waiver in 2012 to support California’s major reworking of its pollution measures into the Advanced Clean Car Rules (earlier post).

Regulatory background. In 1943, Los Angeles experienced its first major smog event. In 1945, the Los Angeles City Health Department established the Bureau of Smoke Control. In 1947, California Governor Earl Warren authorized the creation of air pollution control districts in every county. The Los Angeles County Air Pollution Control District (APCD) became the first of its kind in the state and in the US.

In 1952, Arie Haagen-Smit, a professor of biochemistry at CalTech, discovered the nature and causes of photochemical smog.

In 1955, the Federal Air Pollution Control Act was passed to support a better understanding of the causes and effects of air pollution. The Los Angeles County Motor Vehicle Control Lab and the State Bureau of Air Sanitation were established. Legislation in 1959 enabled California to develop ambient air standards and controls for motor vehicles. The first ambient air standards were established based on observations of health.

In 1960, the California Motor Vehicle Pollution Control Board was established to test and certify motor vehicle emission control devices, while the Federal Motor Vehicle Act of 1960 provided research to address pollution from motor vehicles.

In 1961, the California Motor Vehicle Pollution Control Board mandated the first automotive emission control technology requirements in California and the nation. The first Federal Clean Air Act was passed in 1963. In 1967, California Governor Ronald Reagan (later US President) created the California Air Resources Board by combining the California Motor Vehicle Pollution Control Board and the Bureau of Air Sanitation and Lab. Professor Haagen-Smit became the first ARB Chairman and the first California Ambient Air Quality Standards were published in 1969.

In 1970, US President Richard Nixon signed a new Federal Clean Air Act (CAA)—which included deadlines for meeting air quality goals—and established by executive order the US Environmental Protection Agency (EPA) to implement the CAA. The CAA was subsequently amended in 1975, 1977, and 1990.

The Federal Clean Air Act reserves the control of emissions from motor vehicles for the federal government—with the exception of California, due to its early activity and special conditions (high density of motor vehicles, topography conducive to pollution formation in heavily populated basins—e.g., Los Angeles and the San Joaquin Valley), and any states that opt for the California regulations.

Until California’s pursuit of the waiver for automotive greenhouse gas emission regulations, originally made in 2005, the regulations dealt with criteria pollutants: e.g., NO_x, PM, etc.

In denying the waiver request in 2007, the EPA said that California’s waiver request was distinct from all prior requests, which covered pollutants that predominantly impacted local and regional air quality. The agency asserted that greenhouse gases are fundamentally global in nature, unlike the other air pollutants covered by prior California waiver requests.

Since these gases contribute to the challenge of global climate change affecting every state in the union, the EPA argued, according to the criteria in section 209 of the Clean Air Act, it did not find that separate California standards were needed to “meet compelling and extraordinary conditions.”

However, with the change in Administrations came a change in EPA interpretation. In reaching its 2012 waiver decision, EPA determined that the CARB ZEV amendments were within the scope of prior EPA waivers.