Can Guerilla Warfare target cards that have the word 'hidden' in their text but cannot themselves be set hidden (like Guerilla Warfare itself or Ember Monk)?

Ruling: No, cards must actually have the Hidden keyword and be able to be hidden themselves to be valid targets.

Nuances:

• Cards that merely reference or mention 'hidden' in their text (like Guerilla Warfare or Ember Monk) but cannot themselves be set hidden are not valid targets