I think the only time that you'll be given a warning by a GM is if you're a high lvl char stalking a low lvl char and killing it non stop for hours on end.
I doubt you'll get a warning from a GM for something like that. However, it's likely you will get camped by the guy's lv 85 guild members for some time.
Often there are complaints on the official forums about a lowbie being ganked by the opposite faction, and the usualy response is either get high level friends, suck it up or transfer to a PvE server.