I came across this interaction when thinking about a horse tribal.
Shadowfax, Lord of Horses has this ability:
Whenever Shadowfax, Lord of Horses attacks, you may put a creature card with lesser power from your hand onto the battlefield, tapped and attacking.
Akroan Horse has this ability:
When Akroan Horse enters the battlefield, an opponent gains control of it.
How do these two abilities interact? In a two player game, it seems that Akroan Horse would be an attacking creature, but also that the defending player would have control over it. Is there a rule which removes it from combat when its controller changes?