Reasoning with the Foundations of Rules

Date01 March 2018
Published date01 March 2018
Duncan Wallace*
In PGA v The Queen, the High Court found that a legal rule ceased to exist well before
many people thought it did. In Mabo v Queensland [No 2], the Court found that a legal
rule came into existence well before many people thought it did. These conclusions are
obviously different, and so are the reasons that led to them. But in both decisions the
Court relied on the foundation of a legal rule to account for the rule’s validity over time.
In PGA, the rule was founded on another legal rule. In Mabo, the rule was founded on
an historical fact. I explain how the Court re asoned with these foundations, and what
this reasoning suggests about the nature of the common law in Australia .
This article is about two c ases decided by the High Court of Australia, twenty years
apart. The cases are PGA v The Queen
and Mabo v Queensland [No 2].
They are unrelated
in subject matter. PGA is about the law of rape, Mabo the law of native title. But the cases
are related in the modes of legal reasoning by which the Court decided them, or so I will
In both cases, the Court drew inferences relating to the foundations of legal rules. In
PGA, the Court inferred something from the fact that a legal rule was founded on
another legal rule. In Mabo, the Court inferred something from the fact that a legal rule
was founded on an historical fact. The article explains how these inferences were made,
and why the claim that neither case changed the law in Australia, as some members of
the Court have suggested, is worth taking seriously.
The analysis of the cases here is explanatory. T he article presents a reading of what
the Court did in each case. It d oes discuss some objections to the reasoning in PGA, but
only because those objections, I argue, betray a misunderstanding of the reasoning. And
while I suggest how one of those objections might be revised so that it engages with the
reasoning, I do not commit to endorsing that objection in a revised form.
Section II explains why there is something to be gained from studying PGA and Mabo
side-by-side. The cases both affirm the idea that a legal proposition is discoverable even
* BA (Hons), LLB (Hons) (Monash), LLM (Cambridge). Im grateful to Patrick Emerton for
many discussions about this paper. Thanks also to Jamie Blaker, Sophie Maltabarow, Nathan
Van Wees and the anonymous referees for their suggestions.
(2012) 245 CLR 355 (‘PGA’).
(1992) 175 CLR 1 (‘Mabo’).
50 Federal Law Review Volume 46
where no legal text clearly provides for that proposition. This idea is familiar in legal
theory, if not in legal practice, and is accommodated especially by a theory known as the
declaratory theory of law.
Section III discusses PGA.
Section IV discusses Mabo.
Section V concludes.
This Section makes three introductory points. The first is that inferences have a role in
legal reasoning. The second is that one particular theory of law, the declaratory theory
of law, can be and has been used to make sense of PGA and Mabo. The third is that this
theory, or at least one conception of it, is reconcilable with the drawing of inferences in
legal reasoning.
For some time, the orists have argued that the rules of a legal system are not simply
expressed by authoritative legal texts (for example, statutes and judgments). Legal rules
do not just exist in these texts, waiting for readers to notice them. Of course, the theorists
who believe this have different reasons for doing so. They have different ideas about
what elsethat is, in addition to our legal textsdetermines what the rules are.
For some theorists (who are usually called anti-positivists), that something else is
morality, or an adjudicative exer cise that is bound up with morality.
But one need not
think that morality determines the content of the law to deny that our r ules are
determined only by legal t exts. One might think, as Patrick Emerton has argued, that
our legal system authorises judges to make inferences to work out wha t our legal rules
One of Emertons examples is that judges regularly infer the ratio of a decided case,
and what is only obit er, according to a shared practice. This sort of inference may not
have a moral dimension.
A complication here is that our legal texts might themselves provide for the inferences
that judges can make. Consider the rules of statutory interpretation. These rules seem to
authorise judges to make certain inferences about the opera tion of statutory provisions.
Indeed, the very detail of these rules invites us to ponder whether our legal texts provide
for all of the inferences that our judges make. This is a difficult question and I will not
explore it here.
My point is only that our legal syste m may authorise judgeswhether
via legal texts or notto make inferences to determine what the law is.
This brings me to the declaratory theory of law. In a nutshell, this theory tells us that
when judges decide cases, they apply the existing law and they do not change it.
See, eg, Ronald Dworkin, Laws Empire (Hart Publishing, 1986); Mark Greenberg, The Moral
Impact Theory of Law (2014) 123 Yale Law Journal 1288.
Patrick Emerton, The Centrality and Diversity of the Invisible Constitution in Rosalind
Dixon and Adrienne Stone (eds), The Invisible Constitution in Comparative Perspective
(Cambridge University Press, forthcoming).
For an argument that legal texts cannot stipulate all kinds of legal inference, see ibid.
See, eg, Sir Anthony Mason, Leg islative and Judicial Law-Making: Can We Locate an
Identifiable Boundary? (2003) 24 Adelaide Law Review 15, 18; Allan Beever, The Declaratory
Theory of Law (2013) 33 Oxford Journal of Legal Studies 421, 421; Frank Carrigan, A Blast from
the Past: The Resurgence of Legal Formalism (2003) 27 Melbourne University Law Review 163,
2018 Reasoning with the Foundations of Rules 51
theory is old and worn-out by criticism. Certainly, if one understands the lawas a body
of published rules, the theory is hopeless: we all know that judges change the rules;
indeed, we expect them to do so. But perhaps the theory takes on a more defensible form
when we tinker with our notion of the lawand by extension what counts as a change
to it. This sort of tinkering has given rise to different conceptions of the declara tory
theoryconceptions that go beyond an endorsement of the simple proposition I stated
Not long ago, some alternative conceptions of the theory were reviewed by Allan
Beever, in an article published in the Oxford Journal of Legal Studies.
On one conception
of the theory, the lawmeans natural law, such that positive law can be changed by
judges without c hanging the law, which is in fact rea lizedby these changes.
On this
conception, then, the theory is a kind of natural law theory. On another conception, the
theory says that changes to the law are all made retrospectively, so that the law can be
said to have always been the same as it is now.
On yet another conception of the
theorythe conception that Beever himself defends—‘the lawmeans legal principles of
a certain kind, such as the principle that a debt paid is no longer due. This conception
accommodates changes in legal findings, which, roughly speaking, are the more
particular ways in which l egal principles are applied or enf orced by the courts.
conception has some surface-level resemblance to Ronald Dworkins legal theory, which
at one stage emphasised a distinction between rules (whose application is all-or-
nothing) and principles (w hich have a dimension of weight).
Dworkins distinction
between rules and principles has been criticised as a false one,
and perhaps Bee vers
conception is vulnerable to a similar charge: how are we to tell what is a legal principle
and what is a legal finding?
But let us return to a barer notion of the law as a body of legal rules, without drawing
any distinction between rules and principles. One possible conception of the theory is
that the law include s legal rules which have not yet been published or articulated by our
public officials. That is, it is possible for a legal rule to exist without it appearing in any
of our written laws. So, when a judge relies on a rule that seems novel, she is in fact
revealing some pre- existing content that had just not been written about beforeor so
the theory (on this conception of it) would go. On this conception of the theory, much of
164; Jane Convery, Lord Goffs Swansong: Restitution, Mistake of Law, and the
Retrospective Effect of Judicial Decisions (1999) 3 Edinburgh Law Review 202, 207.
Beever, above n 6.
Ibid 4256.
See Convery, above n 6, 207; Beever, above n 6, 43241.
Beever, above n 6, 42731. The theory is sometimes understood in the performative sense that
judges ‘declare’ the law’s content: see PGA (2012) 245 CLR 355, 420 [178] (Bell J), citing R v P,
GA (2010) 109 SASR 1, 4 [9] (Doyle CJ); Giannarelli v Wraith (1988) 165 CLR 543, 585 (Brennan
J); Kleinworth Benson Ltd v Lincoln City Council [1999] 2 AC 349, 3789; Andrei Marmor, The
Separation Thesis and the Limits of Interpretation (1999) 12 Canadian Journal of Law &
Jurisprudence 135, 142.
Ronald Dworkin, Taking Rights Seriously (Harvard University Press, 1977) 24, 26.
See, eg, Neil MacCormick, Legal Reasoning and Legal Theory (Clarendon Press, revised ed,
1994) 2312; H L A Hart, The Concept of Law (Clarendon Press, 2nd ed, 2012) 25963.

To continue reading

Request your trial

VLEX uses login cookies to provide you with a better browsing experience. If you click on 'Accept' or continue browsing this site we consider that you accept our cookie policy. ACCEPT