- Welker v Hewett (1969) 120 CLR 503 in which the High Court of Australia held that a New South Wales statute (by which it was sought to impose liability for commercial vehicle taxes on directors of companies which owned vehicles, and the company and the director concerned were registered and resident respectively outside New South Wales) was ultra vires because beyond the territorial competence of the parliament of that State.

There were cited to us numerous other authorities, and also text books of authority including Dicey's Introduction to the Study of the Law of the Constitution, the 1924 and 1965 editions. See also Professor DP O'Connell on The Doctrine of Colonial Extra-Territorial Legislative Incompetence (July 1959) 75 LQR 318. We do not lengthen this judgment by further extensive citation, because in our judgment the principles we have already stated are reasonably clear. What are primarily in issue are these questions:

(1) whether these principles apply at all to the States of Guernsey;

and

(2) if they do, whether the Investigation Law of 1991 has any extra- territorial operation;

and

(3) if it has such operation, whether that is no more than is necessary for the good government of Guernsey.