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 Mississippi, as in other states, federal crimes are offenses that fall under the jurisdiction of the federal government, as granted by the U.S. Constitution. These crimes are legislated by the United States Congress and codified in the United States Code (U.S.C.). Federal 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. These offenses are investigated by federal agencies like the FBI, IRS, or Homeland Security and are prosecuted by United States Attorneys in federal courts. State crimes, on the other hand, are prosecuted under Mississippi state law by local or state prosecutors in state courts. It's important to note that some criminal activities can violate both state and federal laws, potentially leading to charges in both jurisdictions.