larry johnson is asking a very good legal question i've not previously seen anyone raise;

Let me explain the meaning of my headline for those of you unfamiliar with the authority of the FBI to investigate Federal crimes while State and local authorities… The FBI does not have the authority to investigate Charlie Kirk’s murder unless there was foreign involvement or a clear violation of a Federal statute. The FBI is a federal agency with nationwide jurisdiction, but it can only investigate crimes that violate federal statutes (codified mostly in Title 18 of the U.S. Code) or that have a clear federal nexus. Typical FBI crimes include:

• Crimes that cross state lines (interstate kidnapping, fugitive flight, human trafficking, large-scale drug trafficking)
• Crimes against federal property, employees, or programs (bank robbery, federal corruption involving federal funds, mail/wire fraud)
• Specifically enumerated federal offenses (terrorism, civil-rights violations under color of law, RICO for interstate organized crime, major cybercrimes affecting interstate commerce, child exploitation material crossing state lines, etc.)
• Major crimes on federal land, Indian reservations, aircraft, or maritime jurisdiction

The FBI does not have general police powers. It cannot, on its own authority, investigate ordinary murder, rape, robbery, burglary, assault, theft, or street-level drug dealing unless one of the federal elements above is present. State and local authorities handle almost all “traditional” street crime and routine law enforcement. The FBI steps in only when Congress has specifically made the conduct a federal offense or when a clear interstate/federal interest exists..........more..........