What do you mean by first person? If you mean make it so they can not switch camera views that is impossible to stop without a client mod.
No, afaik that's handled completely clientside. There's no way to a) detect switches of view mode or b) change view mode.
I am actually not sure if its caused by the block on the sopot of the head, or the actual damage packet, they happend at the same time, when its only the damage part, it does not chance visability when you switch the mode to first person