Suppose that the Court of Appeals for the Ninth Circuit has ruled that a federal law is unconstitutional. Because I live in the Ninth Circuit, I am now allowed to "violate" the law.

What if I do something that would be prohibited by the law, and the US Supreme Court later rules that the law was in fact constitutional? Can I be convicted for having violated the law at a time when it was considered unconstitutional?

2 Answers 2


No. This is covered by the U.S. Constitution by its banning of Ex Post Facto laws from being enforce (i.e. The law cannot be enforced against violations of the law that took place prior to the effective date of the law.). In the event that a lower court rules a law unconstitutional they will typically issue a stay on the ruling for a set date to file with an appeal with a higher court. During that time, the law may still be enforceable, but this is more to make sure the new ruling is properly communicated. The Higher Court may also make a stay pending the outcome of their own decision. However, if the Higher Court does not do this and the lower court's stay expires, it is treated as if the law was never passed, since the ruling in place was that the law is in and of itself illegal to enforce. Thus, if the higher court did not place a stay on the ruling of the lower court and the higher court makes a decision overruling the lower court's decision, than any violation of the law prior to the effective date of the higher court's decision is not a violation of the law.


Can I be convicted for having violated the law at a time when it was considered unconstitutional?

Generally, yes, in any case where ignorance of the law is no excuse, which is the vast majority of criminal cases.

This could be a defense in the rare tiny minority of cases (e.g. willful violation of tax laws in the calculation of the amount due when preparing a tax return, or a law criminalizing disclosure of a class of documents with a certain kind of "top secret" type classification) where ignorance of the law can be an excuse (but even then, only if you 1) were actually aware of the ruling that found the law to be unconstitutional and 2) relied upon that ruling when acting the way that you did).

In any particular case, the constitutionality of a relevant law is a legal issue presented in that case.

Precedents from other cases help courts resolve that issue in your case.

But, this legal issue in your case isn't finally resolved until all possible appeals in your case have been exhausted.

Saying that a law is "unconstitutional in the 9th Circuit" but "constitutional in the 5th Circuit" is somewhat sloppy language and doesn't really mean precisely what taking those statements at face value would actually mean.

  • 1
    Thank you! So it's not entirely safe to "violate" a law that has been struck down unless the Supreme Court has overturned it or affirmed a lower court judgment overturning it? What if the SC denies certiorari?
    – Someone
    Commented Dec 1, 2023 at 23:01
  • @Someone If the controlling precedent at the time your case is filed is that the law is unconstitutional (and it is not a case where ignorance of the law is an excuse), you could still be convicted if the decision holding the law to be unconstitutional is overturned on appeal and the dismissal of the case on grounds of unconstitutionality takes place in pre-trial proceedings before jeopardy attaches.
    – ohwilleke
    Commented Dec 1, 2023 at 23:06
  • Thank you! What if the prosecutor did not file the case until after the law was reinstated? I.e. the law passed, then was struck down, then I violated it, then it was reinstated, then the prosecutor filed charges. I would assume I could be convicted then because jeopardy never attached while the law was held unconstitutional?
    – Someone
    Commented Dec 1, 2023 at 23:49
  • 1
    @Someone Your understanding is correct (subject to the caveats in my other statements about laws for which ignorance of the law is an excuse). These fact patterns might be mitigating factors in sentencing as opposed to guilt or innocence, as they go to degree of culpability and malice and likelihood of recidivism.
    – ohwilleke
    Commented Dec 1, 2023 at 23:52
  • 1
    @Someone: Jeopardy only attaches once a jury is sworn. If the prosecutor files a case against you, and it's thrown out for being unconstitutional, they won't bother to swear in a jury. It would be handled at the motion to dismiss stage, and so in principle there is no constitutional barrier to a subsequent prosecution once the ruling is overturned. In practice, the prosecutors may exercise their discretion to decide whether it is worth bringing the case again.
    – Kevin
    Commented Dec 2, 2023 at 21:33

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