The Effect of Treaty Withdrawal on Implementing Legislation

AuthorElizabeth Brumby
Date01 September 2019
Published date01 September 2019
Subject MatterArticles
The Effect of Treaty Withdrawal
on Implementing Legislation
Elizabeth Brumby*
This article explores the effect of treaty withdrawal on domestic legislation implementing a treaty
in the Australian constitutional context. In R (Miller) v Secretary of State for Exiting the European Union
(‘Miller’), the Supreme Court of the United Kingdom held that the executive cannot exercise its
prerogative power to withdraw from a treaty where that withdrawal would frustrate or invalidate
domestic law. This article contends that treaty withdrawal would be unlikely to have this effect on a
law implementing a treaty in the Australian context. The article ultimately draws two conclusions.
First, a law implementing a treaty would likely survive treaty withdrawal in most cases due to the
law’s enduring nexus with Australia’s foreign relations, enabling its continued characterisation as a
law ‘with respect to’ s 51(xxix) of the Constitution. Secondly, in the event that withdrawal does
lead to a loss of constitutional support, the law would likely become prospectively invalid from the
date of effective withdrawal (an outcome identical to legislative repeal in its effect). The article
contends that this outcome would not, however, engage the constraint on executive power so
emphatically reasserted in Miller. This is because the law’s invalidity is consistent with the implied
will of the legislature and thus reinforces, rather than contravenes, the fundamental principle of
parliamentary sovereignty which the constraint on executive power protects.
I Introduction
The decision of the Supreme Court of the United Kingdom in R (Miller) v Secretary of State for
Exiting the European Union (‘Miller’)
has been characterised as ‘a victory for Parliament over the
executive: of the prioritisation of considerations of democracy and accountability and ...a reaf-
firmation of parliamentary sovereignty itself’.
In holding that the executive could not trigger the
process of withdrawal from the European Union without parliamentary authorisation, the Court in
Miller reaffirmed a constitutional principle of significance for dualist legal systems beyond the
United Kingdom: the executive cannot exercise its prerogative power to withdraw from a treaty
where that withdrawal would alter or destroy domestic law.
Similar scenarios have arisen in other
jurisdictions: last year, South Africa revoked its notification of withdrawal from the Rome Statute
* BA, BCom, JD (Melb), LLM (Cambridge). I thank Professor Peter Cane, Luke Chircop, Tim Higgins, Chris Tran,
Kevin Roche and Will Ken nedy for their invaluable cont ributions to this article. The au thor may be contacted at
Federal Law Review
2019, Vol. 47(3) 390–419
ªThe Author(s) 2019
Article reuse guidelines:
DOI: 10.1177/0067205X19856502
of the International Criminal Court after the executive’s purported withdrawal was held by the
High Court to be unconstitutional and invalid.
In so holding, the High Court emphasised that to
allow the executive to terminate existing rights and obligations without first obtaining parliamen-
tary approval would constitute a conferral of legislative power on the executive, thus contravening
the separation of powers and the rule of law.
Fundamental to the decisions of both the Supreme Court of the United Kingdom and the High
Court of South Africa was that the act of treaty withdrawal in each case would have had the effect
of invalidating national implementing legislation, thereby terminating existing rights and obliga-
tions under domestic law. This effect is what was said to render the executive act beyond power, as
it is contrary to the well-established principle that the executive cannot dispense with domestic
The thesis of this article is that withdrawal from a treaty would not necessarily have this
effect on domestic legislation enacted to implement that treaty under Australian law. While one
prominent public law scholar has suggested that Miller may have implications for the scope of the
executive power to withdraw from treaties in the Australian context,
this would only be so if the
effect of withdrawal would be to render the relevant implementing statute invalid. This article
critically considers this assumption and the constitutional principles that both support and under-
mine it, finding that two fundamental questions arise in relation to the distinctive features of the
Australian Constitution that have not yet been seriously analysed by the courts or the academy.
The first is whether a law initially enacted to implement a treaty could nonetheless sustain its
constitutional validity if that treaty was subsequently altered or terminated — a question that has
been contemplated by one member of the High Court of Australia, but never considered by a
majority of the Court.
The scope of Commonwealth legislative power in Australia is constrained
in a way that legislative power in t he United Kingdom is not, by virtue of having a wri tten
constitution with specifically enumerated heads of legislative power. Parliament may enact a law
implementing a treaty domestically only because such a law falls within the ambit of the legislative
grant of power conferred by s 51(xxix): the external affairs power. Though case law indicates that
the validity of legislation giving effect to a treaty is at least initially tied to the question of whether
that legislation adequately conforms to the agreement it is said to implement,
it is less clear
whether that legislation could remain constitutionally intact, support ed by the external affairs
power, in circumstances where the treaty is later terminated. This article contends that this depends
on two factors: first, the relationship between the various ‘limbs’ of the head of power and possible
doctrinal limits that may attach to these limbs; and secondly, the precise statutory method by which
the treaty has been incorporated into domestic law.
The second question is whether a law that was validly supported by a constitutional head of
power at the time of its enactment could subsequently become invalid due to a changed state of
affairs. In other words, if withdr awal from a treaty does destroy the connection b etween the
implementing legislation and any supporting head of power, does it necessarily follow that that
law becomes invalid from that date? Members of the High Court have suggested that such notions
of ‘creeping unconstitutionality’ are unorthodox, and that the rule of law tenets of stability and
legal certainty require validity to be assessed at, and only at, the date of enactment.
Yet this
position is difficult to reconcile with cases challenging the continuing validity of legislation made
under s 51(vi) (the defence power) following the First and Second World Wars. Judicial statements
in these cases suggest that where a grant of legislative power supports the making of a law based on
a particular set of conditions, the relevant law purporting to exercise the power has no valid
operation once those conditions cease to exist.
This result has been explained in the cases both
Brumby 391

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