This is an important question with a clear answer under Kuwait's Penal Code. Article 14 establishes the baseline rule: you are judged under the law that was in force at the time the act was committed. A new law creating a criminal offence cannot be applied retroactively to punish you for something you did before that law existed.
However, Article 15 provides a significant exception in your favour: if a more lenient law is passed after you committed the act but before a final verdict is reached, the more favourable law must be applied to your case. Even more notably, if a law is passed after your final conviction that completely decriminalises the act, that new law must be applied and the sentence must stop being enforced — even if you are already serving it.
There is one exception to this leniency principle under Article 16: if the law under which you were charged was a temporary law (valid for a fixed period) or one enacted due to emergency circumstances, it continues to apply to acts committed during its validity period, even after it expires or is repealed. As an expat navigating a criminal matter in Kuwait, always ask your lawyer whether any relevant laws have changed since the alleged offence, as this could significantly affect your case outcome.
This is general legal information, not legal advice. For advice on your specific situation, consult a lawyer licensed in Kuwait.