Why, for the love of god, would we leave the EU and then still want to be subject to the rulings of the ECJ? We will not be a member of the EU anymore.
Does the ECJ run its sticky fingers over the dealings with Canada, Japan, Russia? . . . in fact any Country that is not part of the EU.
Are you trying to say that, whether we are in or out, any dealings we have with any EU Country have to be ratified and 'passed' by a court consisting of EU members, dealing with EU members, which presides over ensuring one EU member isn't being 'ripped off' by another EU member?
If that's the case, what is the equivalent UK court that ensures this Country isn't overwhelmed by cheap foreign imports that decimate our own manufacturing & industry . . . oh hang on, we're 40 years too late