Can a Notary Public legally refuse to notarize a signature from a properly identified individual ?
Well, it’s up to the Notary Public to decide what is properly identified. If the notary has any reason to believe that the person is not who they represent themselves to be, they’re obligated to not notarize the document. That’s completely within their discretion. There’s nothing preventing you from going to another notary, though. But if every notary you go to gives you the same reaction, there’s probably a serious problem with your credentials.