Several members of this forum are police officers in their real lives, so I'm not about to get into an "I hate cops" debate. <img src="/images/graemlins/wink.gif" alt="" />
But regardless of the personality of this particular off-duty peace officer, if he knowingly overrode the medical instructions of a qualified, off-duty paramedic and thereby caused injury to any of the casualties, he opened himself and possibly his department up to a lawsuit.
At this point, if I were in Matt's position, I would probably go to my governing/licensing body and seek clarification. I find it ridiculous that he would jeopardize his professional certification by staying to help, but not by abandoning a casualty to the care of someone who was clearly incompetent. If that is, indeed, the case, then perhaps it's a situation that needs to be amended. If it's not the case, then perhaps the licensing body would be willing to issue a clarification in writing, as it's unlikely Matt would be the only one who'd have trouble knowing what to do in these circumstances.
Although I think it's a great compliment to the members of this forum to be asked for their opinion on something like this, it's really a question best answered by the ethics committee of the official certification body.
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"The mind is not a vessel to be filled but a fire to be kindled."
-Plutarch