Forum:Creature Swap vs. Immunity

My opponent controls Felgrand the Divine Dragon Knight and I control Giant Rat in ATK position. I activate Creature Swap, and since he only controls Felgrand he has to swap control. However he chains the Effect of Felgrand to detach a material in order to make it immune to Spell and Trap cards and claims that it's now unaffected by Creature Swap, making Swaps' effect disapear

Can he do that? Up to that point I was certain that Creature Swap affected Players, not monsters (weird way of putting it, but I couldn't think of a better expanation) and was therefore safe of cards like Forbidden Lance or Felgrand. It seems odd to me, but I just wanted to ask if was actually possible. - BronzeJohnson (talk • contribs) 20:23, May 18, 2014 (UTC)