Federal crimes are criminal offenses based on legislation (laws or statutes) enacted by the United States Congress and published in the United States Code (U.S.C.). Most crimes (murder, rape, assault, burglary, etc.) are prosecuted under state law (statutes) and are known as state law crimes. In contrast, crimes prosecuted under federal law are known as federal crimes.

Federal crimes generally involve a subject over which the United States Constitution gives the federal government—and more specifically, the U.S. Congress—the power or authority to legislate or make laws. This power or authority is also known as jurisdiction.

For example, the federal government (and not the states ) has the exclusive authority to print money and regulate its value. And because bank deposits are guaranteed (insured) by the federal government (FDIC) up to $250,000 per depositor, per FDIC-insured bank, and per ownership category, bank robbery is a federal crime (18 U.S.C. §2113). Examples of other federal crimes include tax evasion, wire fraud, mail fraud, immigration offenses, voting or electoral fraud, counterfeiting money, espionage (spying), and damaging or destroying mailboxes.

In Maine, as in all states, federal crimes are offenses that fall under the jurisdiction of the federal government, as outlined by the United States Constitution and federal statutes found in the United States Code (U.S.C.). These crimes typically involve matters that transcend state boundaries or impact federal interests, such as counterfeiting currency, bank robbery due to federal insurance of bank deposits, tax evasion, and mail fraud. Federal crimes are prosecuted by the United States government, often by attorneys from the Department of Justice, including the U.S. Attorney's Office. The federal court system handles the prosecution and adjudication of these offenses. It's important to note that while most common crimes like murder and assault are usually prosecuted under state law, they can become federal offenses if they involve federal jurisdiction, such as crimes occurring on federal property or crossing state lines.