The Executive Branch is responsible for implementing most laws passed by the Congress. Agencies in the executive branch issue rules, make adjudications, and provide other opinions and guidelines in an effort to implement the laws. The Administrative Procedures Act (APA) governs these activities.

The President also has the power to issue executive orders. Executive orders are Presidential directives governing actions by other federal officials and agencies. The President's authority over the executive branch is limited only by the Constitution and federal statutes.

Rulemaking
Under the APA, any agency decision that sets binding obligations or standards for a class of people is a "rule." Rulemaking is particularly important in technical areas, such as environmental law, where the Congress has historically delegated broad discretion to the agencies to implement the statutes. Most administrative rules go through a process known as notice and comment rulemaking. Before issuing most rules, the agency must issue a notice of proposed rulemaking in the Federal Register. This notice must describe the proposed rule and give the public at least thirty days to provide comments. After receiving the comments, the agency can issue a final rule, along with a general statement describing the rule's authority and purpose. Because the agency is required to consider all non-frivolous comments, the agencies will often respond to comments in issuing a final rule. Rules made by regulatory agencies have the force and effect of legislation. Any interested party that participates in the rulemaking can challenge the legality of the rule in a court.

Adjudications
The second major type of agency action is an adjudication. Adjudications occur where the agency is making a binding, case-specific decision, such as sitting, permitting, or licensing a particular activity or facility. In such instances, the agencies are acting like courts in making decisions that settle specific disputes between parties or between the government and a party. Under the APA, these adjudications must be made "on the record after opportunity for a hearing." Any party to the adjudication can typically appeal the decision for judicial review.