Criminal law
Published on June 25th, 2026
The half of the principle everybody remembers is that nobody is punished under a law that did not exist when they acted. For conduct already committed, the starting point is the law in force at the time. The other half runs the opposite way and gets forgotten. Where the later law is more lenient, it applies backwards, which is what lawyers call favorable retroactivity, or lex mitior.
Organic Act 1/2026 of April 8th, on habitual reoffending, brings this into focus, having amended the Spanish Criminal Code, including articles 22 and 66, and come into force on April 10th, 2026. Any matter resting on earlier conduct now has two candidate wordings and one question that comes before all the others.
The Criminal Code provides that more favorable criminal laws have retroactive effect, even where a final judgment has been handed down and the person is already serving their sentence. Where there is doubt as to which law is more favorable, the defendant must be heard (article 2.2 of the Criminal Code). Applied to a reform, that means:
The third of those does the work, since the direction of a reform settles nothing on its own. The 2026 reform touched the aggravating circumstances (article 22) and the rules for determining the sentence (article 66), in particular the treatment of reoffending. Taking that reform as the example, someone is tried today for habitual-reoffending conduct committed, say, in January 2026, before Organic Act 1/2026 came into force on April 10th. The trial happens after the reform, and the tougher wording still does not apply. What governs is the wording that predates it, as the more favorable one and the one in force when the conduct took place.
Run the rule the other way and it reaches further than most people expect. If a future reform softened that same treatment, whoever had committed the conduct beforehand would benefit from the newer and more lenient wording even with a final judgment already handed down, as favorable retroactivity reaches a conviction already given. Either way, I compare the two versions with care before taking anything for granted.
Before settling on a position I check what the provision said on the date of the conduct and compare it with the version in force, to see which law applies and whether there is room for lex mitior. Every citation is checked against its official source, the BOE, before I take it as good.
If you have criminal proceedings open over conduct predating a recent reform, I need the exact date of the conduct before anything else, and from there I can tell you which wording works in your favor. The rest of my work is in criminal law. If you need the matter handled in English, see criminal defense in Barcelona.
Editorial responsibility: Carles Jiménez, Spanish lawyer (Barcelona Bar No. 34.946). This note was prepared with the assistance of artificial-intelligence tools and reviewed and approved by the author before publication.
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