Who gets to determine if you lie? What constitutes a lie? Can I say that the holocaust never happened, if that is what I actually believe? How about global warm

Who gets to determine if you lie? What constitutes a lie? Can I say that the holocaust never happened, if that is what I actually believe? How about global warming. Besides it only takes a marginally more more skilled speaker to get the same result and say nothing at all that can be stated as a direct lie.