The Effect of Treaty Withdrawal on Implementing Legislation

Abstract

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.