If there's no known offence either in directly citable case law, or explicitly defined in legislature-ratified statute, then where can a judge gain the power to define a novel offence on which to condemn someone's conduct?
Before the tort of trover existed, ie before it was defined in common law by a judge, how could the first judged perpetrator have known that it was illegal before they did it?
I mean it seems like that is actually a lot more leeway than judges now have to introduce novel concepts as axioms into their common law canons. Nowadays judges don't have a power to "create law" other than in case of an ambiguity or lacuna if there's no such offence defined in statutes or precisely citable precedents. Why did judges in the past have the power to arbitrarily define new torts and coin/make up words to name them, but seemingly not judges today? What gave them the power to do so and then what took away that power? Doesn't that remove the principle of legal certainty?