Отвечал в другой ветке, но пусть будет ответ и здесь.
Покопался я на форуме ФФГ и нашёл ответ от ФФГшников:

"I have a question about Emperor Palpatine's "Emperor" ability. If Palpatine's player uses "Emperor" on an opponent's hostile figure, who then controls that attack? Special Rules, pg 8 of Heart of the Empire, seem to say Palpatine's player would. However, since "Emperor" doesn't actually say "perform an attack with that figure", and instead says, "That figure interrupts to perform an attack.", many have stated that the special rules on pg 8 don't apply. Who performs the attack when Palpatine uses "Emperor" on a hostile figure?"

If you choose an opponent’s figure with Emperor, that opponent would still control the attack. Emperor doesn’t include the magic word “with” (see the eighth bullet under Special Situations Regarding Attacks on page 6 of the Rules Reference Guide).

The rules for attacking with a Rebel figure are included in the Heart of the Empire rulebook for the 4XP Imperial Class card Embrace Suffering from the Power of the Dark Side class.