The reality of the modern view can be seen in practical operation: under the old "ancient unwritten universal custom" view, (a) jurisdictions could not logically diverge from each other (but nonetheless did), (b) a new decision logically needed to operate retroactively (but did not), and (c) there was no standard to decide which English medieval customs should be "law" and which should not. All three tensions resolve under the modern view: (a) the common law in different jurisdictions may diverge, (b) new decisions may (but need not) have retroactive operation, and (c) court decisions are effective immediately as they are issued, not years later, or after they become "custom", and questions of what "custom" might have been at some "ancient" time are simply irrelevant.