Retroactivity and Ex post facto Principles: Canada, Ireland, and the United States

 

Dear Professor:

I think you have framed the question wrong. Your question is not really about the application of the Canadian Constitution’s Notwithstanding Clause—rather, it is about retroactivity and changes in the “law” (as made by courts, legislatures, and Canadian-ministers’-orders & Presidents’/Governors’-executive-orders) during the course of civil and criminal litigation. 

In the United States and (as I understand it) and in Canada, if a defendant is sued civilly or prosecuted criminally, while his case has not reached final judgment and while all appeals and all ability to seek reconsideration is not yet passed, if the law changes, the defendant can take advantage of such changes in the law if they are to his advantage/benefit. If the case is not final, and the law changes to his disadvantage, if the matter is criminal, ex post facto and retroactivity protections preclude the government from expanding liability/punishment or reducing the evidentiary burden on the state to secure conviction. But if the matter is civil, then the plaintiff might secure the benefit of a change in the law to the defendant’s disadvantage.

It is altogether different if a matter has reached final judgment and all appeals and all opportunities to seek reconsideration have been exhausted (or the time to seek such reconsideration/appeal has passed). If the matter is criminal, then a favourable change in the law, that is, “new” law, by whatever means—legislation, or court judgments, etc, leaves the prior conviction intact or unaffected. If the defendant seeks to re-open the case or seeks habeas review, he is unlikely to secure the benefit of “new” law. In the United States, see FIORE v. WHITE (US 1999 and 2001), in Canada, see R v SARSON (Canadian Supreme Court 1996). Similar principles apply here (in Ireland) too. See A v GOVERNOR OF ARBOUR HILL PRISON [2006] IESC 45 (Irish Supreme Court).

As to the application of the Canadian Constitution’s Notwithstanding Clause—that (in my opinion) may amount to changed or “new” law. If a Canadian defendant were convicted during the tail end of a 5-year period under a criminal statute insulated against Charter-related judicial review (via application of the Notwithstanding Clause), and while that case was under appeal, and the 5-year period ran out, then an appellate court could apply the Charter, strike down the law under which the defendant had been found guilty, and then proceed to overturn the conviction (and any sentence).

If the defendant were convicted and then his appeals and opportunities to seek reconsideration ran out, and then after his conviction was finalized, and then the 5-year period ran out, here the law under which he was convicted would no longer be enforceable going forward (as the courts would not be barred by application of the Notwithstanding Clause), … in these circumstances, it would seem that his conviction would be insulated against any collateral attack or habeas review. The defendant’s conviction would not be overturned.

All this might strike one as unfair...but equal treatment under the law will always have quirky results if the legal system changes the law ... such temporal changes will naturally produce unequal results.

Does that help?

Seth

Seth Barrett Tillman, ‘Retroactivity and Ex post facto Principles: Canada, Ireland, and the United States,’ New Reform Club (Oct. 2, 2026, 6:40 AM), <https://reformclub.blogspot.com/2026/10/retroactivity-and-ex-post-facto.html>; 

See also: Seth Barrett Tillman, Tillman on the Conventions of the Canadian Constitution, New Reform Club (June 6, 2018, 9:28 AM), <https://reformclub.blogspot.com/2018/06/tillman-on-conventions-of-constitution.html>.