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Introduction to U.S. Law & Policy 

U.S. Government Structure

The United States (US) Constitution defines the three branches of the US Federal Government and their powers, as well as the powers that are reserved to the States and to individuals. Under the Constitution, the Federal government of the United States is divided into three parts:

  • The Legislative Branch, or Congress, which is comprised of the House of Representatives and the Senate
  • The Executive Branch, which includes the Executive Office of the President and the Federal agencies
  • The Judiciary Branch, which includes the Supreme Court and Federal Appellate and District Courts

Laws are written and passed by the Legislative Branch, signed and implemented by the Executive Branch, and can be challenged through the Judiciary Branch. The President, as head of the Executive Branch, holds the power to direct the activities of Federal Agencies as long as instructions do not come in conflict with decisions of other branches.

The many types of legal instruments in the US are a product of this three branch system. The types of legal and policy instruments discussed on this website generally come from the Legislative and Executive Branches of government.

The most common types of legal instruments discussed are laws and regulations. Laws are passed by both branches of Congress and signed by the President. Laws establish requirements or prohibitions. Regulations are published by executive branch agencies to clarify their interpretation of a law and how a law will be implemented. Regulations also state requirements or prohibitions.

Some agencies also publish guidance or other policy statements, which further clarify how an agency understands and implements existing laws and regulations. Guidance and other policy statements describe suggested or recommended actions. Guidance and policy statements do not provide mandatory requirements unless they are incorporated into a regulation or mandated under terms and conditions of an agreement, such as a funding agreement.

All laws must be consistent with the authorities provided under the Constitution, and all regulations, guidance, and policies must be consistent with laws. In addition there are several measures the President can use to direct the actions of the Federal government. The most common types are Executive Orders and Presidential Directives. These Presidential measures state mandatory actions for federal agencies, and must be consistent with the Constitution and laws enacted by Congress.

As a nation, the U.S. also enters into treaties, which govern international behavior or are international agreements on specific topics. In the US, a treaty must be signed by the President or an Ambassador and also ratified by two-thirds of the Senate. Once signed and ratified, the terms of a treaty are also mandatory. In effect, the US agrees to be bound by the terms of the treaty.

All of these documents can be placed in a basic hierarchy. In practice, these relationships can be somewhat more complex, but the chart below shows the basic relationships.






Laws are passed by both branches of Congress and signed by the President. Laws can form the basis for regulations, guidance, and policy. At the most basic level, laws explain what you can, cannot, or must do in the U.S. Laws may identify federal crimes or prohibit civil (noncriminal) behavior. A specific law may apply to individuals, businesses, executive branch agencies, or another defined group. Laws must be enacted and implemented consistently with the U.S. Constitution. Laws can be changed or amended only when Congress enacts, and the President signs, a later law.

When a law is passed by Congress and signed by the President, it is given a Public Law number, formatted as PL-XXX. For example, the Public Health Security and Bioterrorism Preparedness and Response Act is numbered P.L. 107-188. However, once a law passes, it is formally incorporated into the United States Code, which is divided into very broad subject areas, named “titles”. Each title focuses on an area of law, such as Title 18 – Crimes and Criminal Procedure, or Title 7 – Agriculture, or Title 42 – Public Health and Welfare. Within titles, the U.S. Code is divided into chapters, subchapters, parts, sections, paragraphs, and clauses.

Generally, laws in the U.S. Code are referenced by Title, section, and sometimes the subsection. For example, authorities enacted under Title II, Subchapter A of the Public Health Security and Bioterrorism Preparedness and Response Act that authorize regulation of select agents by the U.S. Department of Health and Human Services is codified as 42 U.S.C. 262a.

Public laws can enact new authorities or amend existing laws. If you want to see all the authorities enacted or amended by the law, you would look at the Public Law. If you want to see the most up to date version of a specific legal authority, including all amendments made by subsequent public laws, you would look at the United States Code for that subject.

For more information on U.S. laws, please see the laws section.




Regulations are issued by U.S. Federal government Departments and Agencies to interpret and implement laws passed by Congress. When Congress passes a law directing an agency to perform an action, the Department may issue a regulation further interpreting the language in the law. Not all laws require regulations. Agencies generally can issue, modify, or amend regulations without seeking additional action from Congress. 

For more information on when issuing regulations is necessary, please see The Administrative Procedure Act (5 U.S.C. 552).

Issuing a regulation requires several steps:

  • First, the agency publishes a proposed regulation in the Federal Register for public comment, so that any member of the public can suggest changes or ask questions for clarification.
  • Second, after the comment period closes, the agency considers comments and questions it received, and makes changes to the proposed regulation as it thinks necessary to address the comments and questions submitted.
  • Finally, once those changes are made, the agency publishes the final regulation in the Federal Register. 

The final published regulation holds the force and effect of law, and establishes requirements. If an agency wants to update or change a regulation, it must go through the steps above to do so. Some agencies might have additional steps for issuing a regulation. Agencies may issue an interim regulation or more than one proposed version of a regulation, but all agencies must go through these basic steps to publish a regulation.

For more information, please see the regulations section.



Policy Documents

There are many other types of policy documents issued by the US Government, ranging from Presidential memoranda to agency guidance and policy statements. Each has its own purpose and process for publication, but all must be consistent with existing law.


There are several types of instruments in this group, each of which has its own section on this website:

This page last reviewed: February 15, 2018