US: Regulatory Background

US: Regulatory Background


This page provides an overview of the regulatory agencies and the decision-making process in the United States.

Regulatory Authorities

Environmental Protection Agency (EPA)

Emission standards for engines and vehicles, including emission standards for greenhouse gas (GHG) emissions, are established by the US Environmental Protection Agency. The EPA authority to regulate engine emissions—and the air quality in general—is based on the Clean Air Act, most recently amended in 1990.

  • Organizational Structure – EPA consists of 13 Headquarters Offices and 10 Regional Offices. Each regional office is responsible for the execution of the agency’s programs within several states and territories.
  • All EPA legislation is contained in Title 40 of the Federal Register.
  • The Emission Standard Reference Guide contains federal emission standards for on-road and nonroad vehicles and engines, and related fuel sulfur standards.

National Highway Traffic Safety Administration (NHTSA)

Fuel economy standards are developed by NHTSA, an agency within the US Department of Transportation (DOT). In addition, the agency directs the highway safety and consumer programs established by the National Traffic and Motor Vehicle Safety Act (originally enacted in 1966 and now recodified as 49 U.S.C. Chapter 301), the Highway Safety Act of 1966, the 1972 Motor Vehicle Information and Cost Savings Act, and succeeding amendments to these laws.

In May 2010, EPA and NHTSA issued a joint final rule applicable to passenger vehicles and light trucks covering model years 2012-2016. The regulation mandated a reduction in GHG emissions and a combined CAFE standard of 34.1 mpg by 2016 under the US CAFE combined driving test cycle.

  • Organizational structure – NHTSA’s 10 regional offices deliver valuable highway safety support at the local level. These offices and their staffs help States identify their highway safety problems and evaluate safety programs and activities; provide training to local program managers; and offer NHTSA publications and program manuals, safety promotional materials, and other resources.
  • All NHTSA legislation is contained in Title 49 of the Federal Register.

California Air Resources Board

California is the only state vested with the authority to develop its own emission regulations, although they are still required to apply for a waiver from the federal government. Engine and vehicle emission regulations are adopted by the California Air Resources Board (CARB), a regulatory body within the California Environmental Protection Agency (Cal/EPA). Other states have a choice to either implement the federal emission standards, or to adopt California requirements. States that adopted California Clean Car Standards—including the California LEV II and GHG emission standards—are known as Section 177 States.

For more information, see the California Regulatory Background page.

Regulatory Process

Regulations are mandatory requirements that apply to individuals, businesses, state or local governments, non-profit institutions, or others. Congress passes the laws that govern the United States, but Congress also authorizes federal agencies to help put those laws into effect by creating and enforcing regulations. The basics of the regulatory process are below.


Creating a law

Step 1: Congress Writes a Bill

A member of Congress proposes a bill. A bill is a document that, if approved, will become law. To see the text of bills Congress is considering or has considered, look on the Library of Congress’ THOMAS website.

Step 2: The President Approves or Vetoes the Bill

If both houses of Congress approve a bill, it goes to the President who has the option to either approve it or veto it. If approved, the new law is called an act or statute. An example of this is the Clean Air Act.

Step 3: The Act is Codified in the United States Code

Once an act is passed, the House of Representatives standardizes the text of the law and publishes it in the United States Code (U.S.C.). The U.S.C. is the codification by subject matter of the general and permanent laws of the United States. Since 1926, the U.S.C. has been published every six years. In between editions, annual cumulative supplements are published in order to present the most current information.

Employing a law

Laws often do not include all the details needed to explain how an individual, business, state or local government, or others might follow the law. In order to make the laws work on a day-to-day level, Congress authorizes certain government agencies – including EPA – to create regulations.


Regulations set specific requirements about what is legal and what isn’t. For example, a regulation issued by EPA to implement the Clean Air Act might explain what levels of a pollutant – such as sulfur dioxide – adequately protect human health and the environment. It would tell industries how much sulfur dioxide they can legally emit into the air, and what the penalty will be if they emit too much. Once the regulation is in effect, EPA then works to help Americans comply with the law and to enforce it.

Creating a regulation

When developing regulations, the first thing is to determine if a regulation is needed at all. Every regulation is developed under slightly different circumstances, but this is the general process:

Step 1: Agency Proposes a Regulation

The Agency researches the issues and, if necessary, proposes a regulation, also known as a Notice of Proposed Rulemaking (NPRM). The proposal is listed in the Federal Register (FR) so that members of the public can consider it and send their comments to the Agency. The proposed rule and supporting documents are also filed in EPA’s official docket on

Step 2: Agency Considers Comments and Issues a Final Rule

Generally, once the comments received are considered, the regulation is revised accordingly and a final rule is issued. This final rule is also published in the FR and in EPA’s official docket on

Step 3: The Regulation is Codified in the Code of Federal Regulations

Once a regulation is completed and has been printed in the FR as a final rule, it is codified when it is added to the Code of Federal Regulations (CFR). The CFR is the official record of all regulations created by the federal government. It is divided into 50 volumes, called titles, each of which focuses on a particular area. Almost all environmental regulations appear in Title 40. The CFR is revised yearly, with one fourth of the volumes updated every three months. Title 40 is revised every July 1.


The Clean Air Act, like other laws enacted by Congress, was incorporated into the United States Code as Title 42, Chapter 85. The House of Representatives maintains a current version of the U.S. Code, which includes Clean Air Act changes enacted since 1990.

The legal authority for federal programs regarding air pollution control is based on the 1990 Clean Air Act Amendments (1990 CAAA). These are the latest in a series of amendments made to the Clean Air Act (CAA). This legislation modified and extended federal legal authority provided by the earlier Clean Air Acts of 1963 and 1970.

The Air Pollution Control Act of 1955 was the first federal legislation involving air pollution. This Act provided funds for federal research in air pollution. The Clean Air Act of 1963 was the first federal legislation regarding air pollution control. It established a federal program within the U.S. Public Health Service and authorized research into techniques for monitoring and controlling air pollution. In 1967, the Air Quality Act was enacted in order to expand federal government activities. In accordance with this law, enforcement proceedings were initiated in areas subject to interstate air pollution transport. As part of these proceedings, the federal government for the first time conducted extensive ambient monitoring studies and stationary source inspections.

The Air Quality Act of 1967 also authorized expanded studies of air pollutant emission inventories, ambient monitoring techniques, and control techniques.

See “History of the Clean Air Act” on EPA’s website for more details.

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