It would be
VERY unusual for a penal statute to be construed so as to apply retrospectively (for starters,
Ex Post Facto Law is prohibited by the US Constitution,
Art.1, s.9 which states,
inter alia... No bill of attainder or
ex post facto Law shall be passed...."). Simply stated, if at the present time what you do is NOT positively proscribed by law, it is legal. There is a real problem with retrospective imposition of criminal liability, because, if the act was legal at the time it was undertaken, then there could not possibly be the requisite "intent" to act in a manner contrary to the laws of the Country/State/whatever. As 'most'* penal statutes require both an "
actus reus" (Guilty Act) and "
mens rea" (Guilty Mind, also known as intent), there can be no criminal culpability in acting in accordance with the laws as they stand at the time of the act in question. Insofar as the retrospective imposition of criminal liability, the Courts would be unlikely to uphold the validity of any such legislation, it would be correctly construed as an interference by the Legislative arm of the Government with the Judiciary, and as such it would raise SERIOUS questions with regard to the
Separation of Powers and the
Rule of Law (Read
this from the House of Lords).
* Cf the
Drugs Misuse Act 1986 (Qld), where it was held by the High Court of Australia, that no intent was necessary in order to prove possession of an illegal substance, mere possession was enough (although, despite this it is still regarded via the benchbook that it is necessary for the prosecutor to establish that the person expected or somehow knew of the existence of the parcel, without which
Tabe v The Queen [2005] HCA 59 does not apply, see for example
WA v R [2007] WASCA 42, where the Western Australian Court of Criminal Appeal held that the "
Prosecution must establish an awareness or belief in the likelihood, in the sense that there is a significant or real chance, that the item in question was a prohibited drug" I personally am aware of at least one case where
Tabe has been upheld with that modification, insofar as the prosecution needed to establish that the item that the person knowingly possessed was, to their knowledge, a dangerous drug or that it was reasonably suspected to be so (It was a controlled delivery, where unlike
Tabe the "drug" was in the form of pills, which in this instance were labeled as being paracetamol and could not reasonably be suspected of being a dangerous drug).
