You are certainly free to make up your own definitions for words and speak a dialect that is niche but you will not be effectively communicating when you do. By commonly understood definition criminality is a matter of law.

Well, the dude here hasn't been put on trial, let alone convicted, as far as I can tell from the article. So he's not officially considered a criminal by a government. Yet we all seem comfortable calling him one, so I'd say that it is not, in fact, commonly understood to be exclusively a matter of law.