united-states united-kingdom
What if I did something that was a crime, but has now become legal?
<p>There was a question recently about what happens if I do something that is legal today but becomes illegal in the future. The obvious question is what happens in the opposite case? If I do something today that is a crime by today's laws, and next week the law changes and makes the act legal? </p>

<p>Can I be convicted by a judge for something that is today legal? Where everyone in the court room, including the judge, would be allowed to do it today? Does it make a difference if I got caught before or after the law change? Would a judge have legal leeway (that is it's up to him to decide if I should be prosecuted or not?) If I was already convicted, would I have reasons for an appeal with the argument that my actions are not illegal (anymore)? </p>

<p>According to United States federal law, <a href="https://www.law.cornell.edu/uscode/text/1/109" rel="noreferrer">1 U.S. Code § 109 - Repeal of statutes as affecting existing liabilities</a>:</p>

<blockquote>
  <p>The repeal of any statute shall not have the effect to release or
  extinguish any penalty, forfeiture, or liability incurred under such
  statute, unless the repealing Act shall so expressly provide, and such
  statute shall be treated as still remaining in force for the purpose
  of sustaining any proper action or prosecution for the enforcement of
  such penalty, forfeiture, or liability. The expiration of a temporary
  statute shall not have the effect to release or extinguish any
  penalty, forfeiture, or liability incurred under such statute, unless
  the temporary statute shall so expressly provide, and such statute
  shall be treated as still remaining in force for the purpose of
  sustaining any proper action or prosecution for the enforcement of
  such penalty, forfeiture, or liability.</p>
</blockquote>

<p>So it depends on whether Congress expressly said what to do, and if they didn't say anything, it defaults to being able to still prosecute.  But this only applies to federal laws, not state laws.</p>

<p>There's also an exception to this.  In <a href="https://supreme.justia.com/cases/federal/us/291/217/case.html" rel="noreferrer">United States v. Chambers, 291 U.S. 217 (1934)</a>, the Supreme Court said that a prosecution for a violation of the National Prohibition Act could not be continued.  However, this was a special case, as the constitutional provision (the 18th Amendment) that allowed the act in the first place had just been repealed (by the 21st Amendment).</p>

<blockquote>
<p>Can I be convicted by a judge for something that is today legal? Where
everyone in the court room, including the judge, would be allowed to
do it today? Does it make a difference if I got caught before or after
the law change? Would a judge have legal leeway (that is it's up to
him to decide if I should be prosecuted or not?) If I was already
convicted, would I have reasons for an appeal with the argument that
my actions are not illegal (anymore)?</p>
</blockquote>
<p>Context would matter, but usually, the answer would be yes, you could be convicted, even if you were arrested after the change in the law. The judge would have no say in the matter and this would not generally be a ground for appeal.</p>
<p>For example, suppose that you were charged with failing to honor a curfew imposed in the aftermath of a Hurricane and that curfew has now been lifted. You could still be prosecuted and convicted for violating the curfew.</p>
<p>Similarly, suppose that you are convicted of possessing heroin in 2017, but in 2018 heroin is legalized, and the case against you for possession of heroin is prosecuted in 2019. You could be convicted of heroin possession in 2019 as a matter of federal constitutional law in the U.S., even though many prosecutors would decline to press charges in those circumstances, even though a jury might be inclined to engaged in jury nullification, and even though some state constitutions or state jurisprudence might discourage or forbid this prosecution.</p>
<p>There is something subtly different which doesn't really line up with your question but is easily confused for it.</p>
<p>Suppose that you are convicted of a crime, but after your conviction, a court holds as a binding precedent in another case, that the crime that you were convicted of is unconstitutional or otherwise invalid in your circumstances (e.g. in a U.K. scenario, you are convicted of trespassing on the walkway to someone's front door since that is private property, but a later precedent hold that members of the public are legally entitled to use such a walkway unless there is a &quot;no trespassing&quot; sign posted which no one disputes wasn't present in your case).</p>
<p>As a matter of constitutional U.S. law, your conviction remains valid and you must serve the sentence, if your conviction was final and all appeals had been exhausted when the new court decision was announced unless it was a &quot;new rule&quot; of law rather than a mere interpretation of existing law, but if your conviction was not yet final because post-conviction motions or appeals were still pending, the new rule of law could be utilized to challenge your conviction. Under the U.S. Constitution, &quot;new rules&quot; have retroactive effect, while interpretations of existing law do not.</p>
<p>In France, in contrast, the constitution states that all people convicted of crimes that cease to be crimes under a change in the law, are entitled to benefit from the change in the law.</p>
<p>I don't know what English law says about this question.</p>

<p>Since this is also tagged UK, there's a different answer there.</p>

<p>In Gouarré Patte v. Andorra, the EHCR decided that the most lenient of laws must be applied. In the actual case, Andorra had merely reduced the possible penalty, but in the hypothetical case posed in the question that would mean no penalty at all would be possible.</p>

<p>Note that this is the EHCR, not the EU/ECJ, so this is not affected by Brexit.</p>
