If one of these creatures can’t attack its owner during any given turn (due to a spell or ability such as Chronomantic Escape, or because a player on the opposing team has gained control of it, for example), it may attack another player, attack a planeswalker an opponent controls, or not attack at all. If there’s a cost associated with having that creature attack its owner, you aren’t forced to pay that cost, so it may attack another player, attack a planeswalker an opponent controls, or not attack at all.