I have a guy in my group who seems hellbent that if he grabs an ally, he can teleport with them. Couldn't find anything in the PHB so I'm asking if anyone has any hard evidence against this. Really getting frustrating. Thanks.
You can only bring a grabbed ally along when you teleport if you have teleportation as a movement speed, not if you use a power to teleport.
From the Rules Compendium, p244 (emphasis mine):
Moving a grabbed target is a standard action. Unless you have teleportation as a movement speed and therefore don't need to activate a power to teleport, you can't bring anyone with you; this is because you can't take two different actions simultaneously.