How do you know it was him? There's not much for us to go on. We need to know things such as when this happend, what server it was on, and most importantly, how you know it's him. And it would also be helpful if we knew when his GB runs out, just in case he wasn't evading it.
edit: I'm pretty sure tom was never global banned for anything, he's spoofed a clan tag before this, however.