The President is the administrative head of the executive branch of the U.S. government, which includes numerous agencies and executive departments.
The agencies of the executive branch make administrative law, comprised of rules (also called regulations) and administrative decisions. These have the force of law and are subject to review by the federal courts. Rules are frequently promulgated to implement legislation.
Sources of primary law:
Federal Register: Contains rules and proposed rules of federal administrative agencies published chronologically (published every week day).
Code of Federal Regulations (CFR): Contains rules of agencies that are codified by topic.