Is there an International Rule under which the baggage of a passenger is offloaded in the case that he/she fails to report at the departure gate 15 minutes before boarding time?
This question was covered over on travel.stackexchange and seems like there is a European reg on it.
In Europe, the question is covered by Regulation EC 300/2008. Annex I, section 5.3 reads
Each item of hold baggage shall be identified as accompanied or unaccompanied. Unaccompanied hold baggage shall not be transported, unless that baggage has been either separated due to factors beyond the passenger’s control or subjected to appropriate security controls.
I cant find any hard regulations but there seems to be some discussions floating around that would imply a domestic US flight may depart with your bags and without you here in the states.
I can speak from experience while on a flight departing CDG for DUB the plane was held to remove a bag that belonged to a passenger that decided to take a different flight.