What are the differences between federal and state crimes?
The U.S. Constitution allows states the power to govern themselves, but where the entire nation’s welfare is concerned, Federal law trumps state law. This is under the Supremacy Clause of the U.S. Constitution. Some areas of criminal law are concurrently occupied by both state and Federal laws, but a state statute which contradicts a Federal law, will be ruled “unconstitutional” by a Federal judge and nullified. The Feds may also regulate a certain area of criminal law exclusively, so that they are said to have pre-empted the field. One example would be counterfeiting of money. You can see what chaos would follow if each state were allowed to regulate and issue their own money. Areas of law not occupied by the Feds are reserved exclusively to the states.
The Federal Interstate Commerce clause often grants the Feds criminal jurisdiction. That clause gives the Feds sole power to govern interstate business issues such as telephone, television, trucking, U.S. Mail, and air travel, to name a few. It’s the reason that sex with a minor becomes a Federal crime if she is taken over a state line. Other areas of criminal law that will invoke Federal jurisdiction are national security, the military, the Post Office, Federal Taxes, and Federal benefit entitlement programs. Graffiti is a local crime, but not if it’s on a Post Office building. Similarly, tax evasion or tax fraud, evading the military draft, breaking into a National Guard armory, or Welfare Fraud can all wind you up in Federal Court.
What about this? Joe gets drunk in San Francisco, drives to Las Vegas, stops to make an obscene gesture to a Federal Senator, and then he is arrested, still under the influence. Who gets Joe, the Feds or Las Vegas Police? Answer: the locals. His driving across the state line drunk has no national significance to the Feds. He did not threaten the Senator, and has a right to free speech, so his only offense is local drunk driving.
Note: many criminal cases are mixed. The Feds can allow the state to prosecute a small bank robbery. A Federal Prosecutor with a racketeering case can also prosecute a violation of a state murder law involved in their case.