Federal regulations (also called rules) are issued by the executive departments and agencies of the Federal government under statutory authority of the Congress. Because regulations have the force of law and affect in profound ways the daily life of Americans, they are often contentious. Since 1946 the Administrative Procedure Act has laid out the steps the issuing agency must follow in developing the regulation. Importantly the Act allows for judicial review.
The first phase in the process is the issuance of the regulation in a proposed version. All proposed regulations are published in the daily Federal Register. Agencies will preview anticipated rules and proposed rules twice a year in their Unified Agenda, also published in the Federal Register. In their proposed stage, regulations can be modified after hearing comments by interested stakeholders before they become final. Proposed and final rules since the early 1970s have explanatory information in their preamble which can be important in dertermining original intent and understanding subsequent amendments.
Regulations are arranged by subject and published in a code called, naturally, the Code of Federal Regulations (CFR). Only final regulations are added to the code. Proposed regulations are in the Federal Register or in an unofficial commercial service published for practitioners in a particular field: tax, securities or the environment for example. In between yearly printing of the CFR new added regulations are listed in a slim volume called the List of Sections Affected (LSA). A quick check of the annual LSA can determine if a regulation was changed in the interim.