The Billiard Parlor says-
Controller React, Boot: After posses are formed, for the remainder of the shootout, hand ranks cannot be modified Shootout, React, or non-Cheatin' Resolution abilities. Dudes cannot be discarded or aced by Shootout or non-Cheatin' Resolution abilities during the first round.
Decimator Array doesn't raise or lower hand ranks, it alters the composition of the hand that then provides the hand rank.
Hand ranks are modified by cards like Force Field or Outgunned- ie, 'increase your hand rank', or '+1 hand rank', or 'lower your opponent's hand rank'.
Hopefully this clears things up, but I'll leave this unlocked in case there are follow up questions.