If an opponent plays Possession on a unit and the unit is Flashed back to base in response, does the opponent still take control of it?

Ruling: No, the opponent will not take control of the unit. If the unit is no longer at a battlefield when Possession resolves, it will not take control of the unit.

Nuances:

• This works the same way as cards like Hidden Blade and Void Seeker, which also fail to affect units that are no longer at a battlefield when they resolve
• Even though Possession's text structure separates "Choose a unit at a battlefield" from the control effect, the unit still needs to be at a battlefield for the effect to resolve