7.1 People should generally not be prosecuted for conduct that was not an offence at the time the conduct was committed. If on Wednesday it is not an offence to go fishing at Bondi Beach, then people will usually expect that a law will not be enacted on Thursday making it an offence to have gone fishing the day before. But this principle does not only apply to criminal laws. More generally it might be said that laws should not retrospectively change legal rights and obligations.
7.2 This chapter discusses: the source and rationale of limiting retrospective laws; how the principle is protected from statutory encroachment; and when retrospective laws may be justified. The ALRC calls for submissions on two questions.
Question 7–1 What general principles or criteria should be applied to help determine whether a law that retrospectively changes legal rights and obligations is justified?
Question 7–2 Which Commonwealth laws retrospectively change legal rights and obligations without justification? Why are these laws unjustified?
7.3 The common law on the subject of retrospective law making was influenced by Roman law. It may also be reflected in cl 39 of the Magna Carta (1215), which prohibited the imprisonment or persecution of a person ‘except by the lawful judgement of his peers and by the law of the land’.
7.4 In Leviathan (1651), Thomas Hobbes wrote that ‘harm inflicted for a fact done before there was a law that forbade it, is not punishment, but an act of hostility: for before the law, there is no transgression of the law’. William Blackstone wrote in his Commentaries on the Laws of England (1765):
Here it is impossible that the party could foresee that an action, innocent when it was done, should be afterwards converted to guilt by a subsequent law: he had therefore no cause to abstain from it; and all punishment for not abstaining must of consequence be cruel and unjust. All laws should be therefore made to commence in futuro, and be notified before their commencement.
7.5 Retrospective laws are commonly considered inconsistent with the rule of law. In his book on the rule of law, Lord Bingham wrote:
Difficult questions can sometimes arise on the retrospective effect of new statutes, but on this point the law is and has long been clear: you cannot be punished for something which was not criminal when you did it, and you cannot be punished more severely than you could have been punished at the time of the offence.
7.6 Retrospective laws make the law less certain and reliable. A person who makes a decision based on what the law is, may be disadvantaged if the law is changed retrospectively. It is said to be unjust because it disappoints ‘justified expectations’.
7.7 The criminal law ‘should be certain and its reach ascertainable by those who are subject to it’, the High Court said in Director of Public Prosecutions (Cth) v Keating (2013). This idea is ‘fundamental to criminal responsibility’ and ‘underpins the strength of the presumption against retrospectivity in the interpretation of statutes that impose criminal liability’. The Court then quoted Bennion on Statutory Interpretation, 5th ed (2008):
A person cannot rely on ignorance of the law and is required to obey the law. It follows that he or she should be able to trust the law and that it should be predictable. A law that is altered retrospectively cannot be predicted. If the alteration is substantive it is therefore likely to be unjust. It is presumed that Parliament does not intend to act unjustly.
7.8 In Polyukhovich v Commonwealth (1991), Toohey J said:
All these general objections to retroactively applied criminal liability have their source in a fundamental notion of justice and fairness. They refer to the desire to ensure that individuals are reasonably free to maintain control of their lives by choosing to avoid conduct which will attract criminal sanction; a choice made impossible if conduct is assessed by rules made in the future.
7.9 The Terms of Reference refer to both laws that retrospectively change legal rights and obligations and laws that create offences with retrospective application. This chapter deals with both of these types of law, but the second type of law is more difficult to justify. In Retroactivity and the Common Law (2007), Ben Juratowich writes:
Retroactive creation of a criminal offence is a particularly acute example of infraction by the state of individual liberty … Holding a person criminally liable for doing what it was lawful to do at the time that he did it, is usually obviously wrong. The retroactive removal of an actual freedom coupled with the gravity of consequences that may accompany a breach of the criminal law mean that retroactive imposition of a criminal liability is rarely justified.
The Terms of Reference refer both to laws that ‘retrospectively change legal rights and obligations’ and to laws that ‘create offences with retrospective application’. These are treated together in this chapter.
Ben Juratowitch, Retroactivity and the Common Law (Bloomsbury Publishing, 2008) 28. Juratowitch notes however, that this clause is more concerned with placing limits on the exercise of executive power.
Thomas Hobbes, Leviathan (Oxford University Press 1996, 1651) 207.
William Blackstone, Commentaries on the Laws of England (15th ed, 1809) vol 1, 46.
Tom Bingham, The Rule of Law (Penguin UK, 2011).
Lord Diplock said: ‘acceptance of the rule of law as a constitutional principle requires that a citizen, before committing himself to any course of action, should be able to know in advance what are the legal consequences that will flow from it’: Black-Clawson International Ltd v Papierwerke Waldhof-Aschaffenburg  AC 591.
HLA Hart, The Concept of Law (Clarendon Press, 2nd ed, 1994) 276. (‘retrospective law-making is unjust because it ‘disappoints the justified expectations of those who, in acting, having relied on the assumption that the legal consequences of their acts will be determined by the known state of the law established at the time of their acts’)
Director of Public Prosecutions (Cth) v Keating (2013) 248 CLR 459, 479  (French CJ, Hayne, Crennan, Kiefel, Bell And Keane JJ).
Ibid  (French CJ, Hayne, Crennan, Kiefel, Bell And Keane JJ).
Polyukhovich v Commonwealth (1991) 172 CLR 501, 608 (Toohey J).
Ben Juratowich, Retroactivity and the Common Law (University of Oxford, 2007) 52.