If an enemy fighter fails the cool check to not target a model afflicted with the above power in theSeen Unseen (Basic), Continuous Effect:
Choose a single enemy fighter is within 3" of the Psyker. While this power is maintained, the chosen fighter treats all fighters as being enemy fighters, and all fighters treat the chosen fighter as being an enemy fighters.
Note that this means any rule, special or otherwise, the affects friendly fighters or friendly faction fighters ceases to work for the chosen fighter whilst this power is maintained as the chosen fighter has no friendly fighters of any sort on the battlefield.
House of Shadows page 99
Assess Target Priority
phase of shooting (Core Rulebook page 116).Can they opt not to shoot them, i.e. cancel the shot, or are they now required to pick them as the target in the
Declare the Shot
(Core Rulebook page 116) and continue the shooting workflow?