chip time vs. gun time question is clearly stated in the USATF rules.

I have been contacted by some of you concerning how the Salt Lake City Marathon decided on the winners. Here is the actual rule set by USATF concerning chip time. One thing to remember before everyone jumps on the complaint band wagon about the SLC marathon, its organisation, or Devine Racing, they do bring us an opportunity to race here at home in a semi- high profile race that could go away and not picked up by anyone else each year. Even long time big races have problems with courses, timing, award mix ups, financial troubles, media issues, and tons of things you never hear about. In this case, the timing issue or declaring winners at Salt Lake was not handled correctly by rule. And the media loves a story and runs with it and now may have created even a bigger story if they publicly take it back away again and declare the true winner who crossed the finish line first the actual winner.

RULE 245
FINISH LINE RECORDING AND TIMING
1. Officials at the finish should record each number as the athlete completes the
race, along with the athlete’s finish time. The order in which the athletes cross
the finish line will be the official finish position.
2. The timers shall start their watches or timing devices at the flash/smoke of the
pistol or approved apparatus or at the first moment a competitor crosses the
start line, whichever happens first. False starts in road races should not be
recalled.
3. The official time shall be the time elapsed between the start of the watches or
timing devices resulting from an appropriate start signal and when the athlete
reaching the finish line. The actual time elapsed between when an athlete reaching the starting line and finish line can be made known to the athlete, but will
not be considered as official time.