Because Congress passed a law making it a federal crime to murder American citizens abroad.
Which is nuts! “Bailiwick”, “Jurisdiction”... Apparently, ALL of that is out of the window now. Of course, now that I remember it... this seems to coincide with the fed gov allowing interpol to set up offices around our country with agents who are NOT constrained by our “Constitution” (NOT, that the fbi and federal courts give much of a rat’s rear about it)! GLOBALISM. We’ve lost our liberty!