In order for the government to have power to regulate any kind of behavior, it must have “jurisdiction.” In most cases, jurisdictional issues are straightforward—the crime occurs within a particular state’s boundaries, violating that state’s laws, and therefore giving that state the power to prosecute. Likewise, a crime that occurs on federal property—for example, Yellowstone National Park—authorizes the feds to deal with the suspect. But some crimes violate both state and federal law, enabling both governments to bring criminal charges. (Some crimes, on the other hand, are left only to the states—see Supreme Court: Why a Love Triangle Isn’t Chemical Warfare.)
As long as there is a sufficient federal “nexus,” the United States government can regulate almost any kind of behavior. That means, for example, that it’s possible to violate federal law through conduct that occurs solely on one state's land. For instance, the federal government has authority under the U.S. Constitution to regulate interstate commerce. Crimes with sufficient connection to interstate commerce—for example, transporting a stolen vehicle between states—are therefore properly federal offenses. (United States v. Peters, 952 F.2d 960 (7th Cir. 1992).) Oftentimes, the connection to interstate commerce is rather slight.
Example: Eight men try to rob a racetrack in Illinois, but are thwarted by security guards. In their subsequent prosecution for attempted robbery, they argue that the federal government doesn’t have jurisdiction to prosecute them because the alleged crime occurred on state grounds. But because the racetrack’s money is federally insured, many of the horses’ owners come from out of state, and the track uses several out-of-state services (for betting machines and advertising materials, for example), jurisdiction was properly vested in the U.S. government. (See United States v. Harty, 930 F.2d 1257 (7th Cir. 1991).)
In many instances, one government with jurisdiction over an offense will defer to another. The deferring government will step in only if the other prosecution fails. That said, sometimes both governments will pursue criminal charges.
Example: In 1991 in Los Angeles, several police officers were involved in the vicious beating of motorist Rodney King. Because of the case’s tremendous publicity, the court changed venue to Ventura County in Southern California. The Ventura jury acquitted the officers on all but one charge (as to which it hung), sparking the 1992 Los Angeles Riots. Months later, a federal grand jury indicted the officers for the same beating under a law punishing anyone who, acting under governmental authority, violates another person’s federal rights. (18 U.S.C. § 242.) A federal jury ultimately convicted two of the four officers under the U.S. law, which prosecutors frequently invoke in excessive force cases. (To read about a similar situation, see Federal Charges in the Kelly Thomas Case?)
Example: Federal authorities charged NFL quarterback Michael Vick for running an interstate dog-fighting business that involved dog executions and gambling, among other illegalities. A federal court sentenced him to 23 months in prison. The state of Virginia separately prosecuted Vick for the dog-fighting ring. After his federal conviction, while he was still in U.S. custody, he pleaded guilty to a state charge. (The sentence for the state crime was essentially folded into the federal sentence he was serving.)