That is unfortunately not the case. There is always a method to do that. Whether it is hacking through your IP, or just faking it in general. My knowledge of computer hacking is limited, but the possibilities I know of are definitely possible. I have heard of it being done, and even gone through and looked into it myself. All you have to do is go through another IP. That is difficult and you have to have vast computer knowledge to pull it off, but it is possible. This may not have happened on Minecraft yet(it is possible that it has happened just isn't in the public yet), but if VPN bans become possible then it will likely become public.