Yeah I figured as much since those pokemon aren’t in the game and the only way to get them legit is by trade. I already have those pokemon, but I got them through a wild pokemon modifier. Now I did find a code here that will give you Regice, Registeel, Regirock in your pc box that was posted by Gr8trainer , but I don’t know if they are legit the code is for heart gold, but it works on soul silver, plus they are shiny and it states they are from the Hoein region, but I don‘t know if that legit enough.
http://projectpokemon.org/forums/showthread.php?9359-Riolu-Aura-Sphere-Now-s-Pokemon-SoulSilver-amp-HeartGold-Action-Replay-Codes/page83