In an interview Orton said it was legitimately banned because he has actually smacked some guys pretty hard with it (claims to have given a Vince a concussion). I don't see why they need to ban it though because he only hit it once every few months anyway. I guess Big Show was an exception at ER.
Orton himself said it was banned, they allowed him to use it at Extreme Rules because he was in his hometown. It's a shame though, the punt was a big part of his character, now he's like...a viper without teeth.