First, no one has yet established in any way shape or form, that the law would consider you to have sole ownership of a character concept that exists in a shared imaginary world, especially one where other participants may (in some circumstances, depending on the rulestet, table etiquette, etc) be expected, in the normal course of play, to exert control over that character, and whose behaviour and history is likely to combine elements provided by multiple participants, both indirectly and directly.
If you do feel that IP Law applies in this instance, that also means you can't play any pre-existing imaginary character without the IP-holder's explicit permission. Are you contending that if I choose to pretend to be Harry Potter in the privacy of my own bedroom lounge room while conducting normal TTRPing, that I am in breach of IP law? If not, then I don't see what IP Law has to do with any of this.