Is giving an enemy unit back as part of Hostile Takeover able to be reacted to?

Ruling

No, the "lose control" and "recall" effects of Hostile Takeover cannot be reacted to.

These effects are duration-based effects inherent to the resolution of the Hostile Takeover spell itself. Because they are not triggered abilities, they do not use the chain and therefore do not provide an opportunity for players to play reactions.

Reasoning

1. Nature of the Effect: Hostile Takeover is a spell that, upon resolution, creates a state-based duration: "Lose control of that unit and recall it at end of turn." This is a single, continuous instruction defined by the spell's resolution.
2. Triggered Abilities vs. Duration-based Effects:
   • Triggered Abilities (Rule 383) are defined by specific conditions ("When," "At," "The first time") and are placed on the chain as pending items when those conditions are met.
   • The text "at end of turn" in Hostile Takeover is the defined expiration point for the control-changing effect created by the spell.
   • Because this is not a triggered ability, it does not follow the process of being placed on the chain (Rule 383.3). It is an automatic game action that occurs when the turn reaches the Ending Phase.
3. Chain Timing: Reactions can only be played when an item is on the chain (Rule 327). Since the "lose control" and "recall" actions do not use the chain, there is no point at which a player can add a reaction to them.

Summary of the Process

• Hostile Takeover is played and resolves.
• The controller gains control of the unit for the duration of the turn.
• When the game reaches the Ending Phase, the duration expires. The game automatically processes the "lose control" and "recall" instructions as part of the turn's cleanup procedures.
• Because this process does not involve the chain, no reactions can be played in response to the unit returning to its owner's base.

Note: I could not fully verify this ruling against the retrieved rules.