When a unit is played and its 'when you play me' trigger goes on the chain, but then an opponent takes control of that unit with Hostile Takeover in response, who controls the triggered ability?

Ruling: The original player who played the unit remains the controller of the triggered ability. Taking control of the unit does not change the controller of the trigger.

Sequence:

• Player plays a unit with a 'when you play me' trigger
• The trigger is created and its controller is established as the player who played the unit
• Opponent takes control of the unit with Hostile Takeover
• The trigger remains controlled by the original player

Nuances:

• Triggered abilities behave like activated abilities once on the chain
• The controller of a trigger is established when it goes on the chain and does not update in real time
• If controller updated in real time, removing a unit in reaction to its trigger would make the trigger uncontrolled and cause issues with target definitions (like 'enemy')
• Reflexive triggers generated by spells would have no defined controller by the time they finalize if controller updated in real time, since the spell would already be in the trash