It would be interesting to know what precise accidents or
experiences provoke the writing of books and the choice of
topics for academic study. Often the student himself cannot
say. I suspect that the origin of a long-standing fascination by
the idea of sovereignty might, in the present case, be traced to a
first undergraduate reading of the passage in which Sir Ivor
Jennings explains that De Lolme was mistaken in thinking that
Parliament could do anything except make a man into a woman
and a woman into a man; since if Parliament enacted that all
men should be women, they would be women as far as the law
is concerned. The intellectual neatness of this arrangement im-
pressed and convinced me at the time, but I have wondered
ever since why there is (so far as I know) no full-length study of
so curious a constitutional principle.

The present work can hardly make any such pretension. It is
rather an attempt to look at some of the traditional implica-
tions of the sovereignty doctrine in the light of certain ideas about
the function and description of legal rules in theoretical writing
about law, and also of recent constitutional developments out-
side the United Kingdom.

My obligations in respect of encouragement, criticism, and
advice are many. I am deeply indebted on all three counts to
Professor W. J. M. Mackenzie of Manchester, and Howard
Warrender of Glasgow. I also have much kindness and assistance
to acknowledge in Oxford. To Professor H. L. A. Hart and to
Mr. K. C. Wheare, the Rector of Exeter, I owe a debt which
is both personal and one which is shared with all students of
legal theory and constitutional practice.

Many people have helped me to secure important material.
I must acknowledge with gratitude the permission of Professor
E. C. S. Wade and the Government of the Union of South
Africa to reprint and to quote from the legal opinion drafted by
Professor Wade in 1952. In that year a summary of the opinion
was published in the South African daily press, but Professor
Wade has very generously allowed me to see and to make use of

-v-