If Ambipom G uses tail code and moves the energy to a benched pokemon that has Unown G attached, the energy should be moved to that benched pokemon and then discarded. The game currently prevents the energy from being moved. Ruling:
If I use Ambipom [G]'s “Tail Code” attack to move an energy card from the Defending Pokemon to one of my opponent’s Pokemon that has an Unown-G attached to it, what happens?
While Unown-G prevents the attachment of the energy to the protected Pokemon, it does not prevent the removal of the energy card from the Defending Pokemon. The energy card is discarded.
Source: PUI Rules Team (2010-01-14)