Is "Laws can't be retroactive" hard and fast? In the Constitution or just common law?

I know laws can’t be made retroactive.
They can’t make a law that codine is illegal to purchase and then round up everyone who already bought some.
(Although, come to think of it, they can outlaw posession, and have done so as every new street drug becomes popular. But that’s not necessarily retroactive.)

Anyway, where is it written?

Under Article I, Section 9, of the US Constitution -

So does that mean that post facto laws were made before the revolution?
Are they allowed right now in England?

And just for the record: a “bill of attainder” is a law that declares a named person or particular group of people guilty of a crime without any trial. Typically it would also work some penalty on the guilty party’s civil rights such that they could no longer leaglly hold title to property or bequeath anything to his family.

So far as I know, and I welcome correction on this point, the principle of parliamentary supremacy applies to England – Parliament may pass any law it wants to.

The European Convention on Human Rights, Article 7, states:

Now, you’re right about the principle of parlimentary soverignty - the ECHR doesn’t have the force of the US constitution, it’s just another statute law. In theory, Parliament could pass a law which had retrospective effect. However, anyone prosecuted under such a law could go to Strasbourg and get a declaration of incompatibility - the UK would then be obliged to either (a) rescind the law (b) secede from the EU or (c) pay the fines associated with the declaration.

It should also be noted that the Article doesn’t prohibit retrospective legislation, as such. It just says that such legislation can’t make the punishment a person is subjected to to heavier than it would have been at the time of the offence.

Not correct. Only criminal laws can’t be retroactive, because of the ex post facto clause. Other types of laws can be. Tax provisions, for example, are frequently retroactive.

Untrue. Read the constitution. No ex post facto laws can be passed. Period. No law can get around that, no matter what the purpose.

You can be required to pay taxes from previous years (say if you didn’t file a return when you were required to), but those taxes must be on the books at the time you are required to pay.

Congress cannot require, for instance, that you pay taxes on your Internet purchases from 1990-2005. If, however, they pass a law tomorrow that this is required, and it’s found in five years that you haven’t, you are liable for the taxes owed after the law is passed.

From Calder v. Bull, 3 U.S. 386
Justice Samuel Chase wrote:

Cite, Chuck. Retroactive laws are not necessarily unconstitutional. It says so right here in my edition of Black’s Law Dictionary, Eighth Edition, under “retroactive law.” The Ex Post Facto Clause has typically been interpreted to prevent ex post facto criminilization of laws, or extending/enhancing criminal penalties ex post for an already criminal act.

There are lots of restrictions on what kind of retroactive laws Congress can enact, but most of them flow out of the Due Process Clause, as well as the Obligation of Contracts Clause.


Commentary on Chase’s decision in Calder v. Bull:


I’m just presenting this and make no pretense that I agree with the argument or understand the law involved.

So what is a retroactive law that isn’t ex post facto? I can’t see how that’s possible.

California Three Strikes Law, is retroactive but not aparently ex post facto. If you commited a crime that would be considered a strike now, even though you commited it before the law was on the books, it will now be considered a prior strike for sentencing purposes. The really nasty part is where they count crimes commited by juveniles as strike priors.

Another one is DUI. Until last year a prior DUI within 7 years made a current DUI a second offence. Now a prior within 10 years applies. Even if when you were cnvicted they told you it would stay on your record for only 7 years.

IANAL, but retrospective legislation is used in Australia. As a matter of statutory interpretation, judges tend to require Parliament to state very very plainly that their intent is for a law to have retrospective effect.

A recent example is the retroactive excision of certain islands from the migration zone after people seeking asylum had already landed there.

IANAL, but my understanding is that ex post facto punishments are prohibited. But, despite what many argue, taxes are not a form of punishment. So it is legal to tax somebody for ownership of an item that was not taxable when they purchased the item. You just can’t retroactively criminalize ownership of the item.

Alternatively the Government could derogate from that part of the Convention as Bliar had disgracefully done over detention without trial.

This has confused me about new (ish) sex offender laws - where a convicted offender has to be on a register, even if the offence was committed before the law was instated. Doesn’t that count as “extending/enhancing criminal penalties ex post for an already criminal act.”?

I got a speeding ticket last year, and paid the fine etc. I’d be a bit miffed (to say the least) if I then got told “Ah yes, well this new legislation means that the punishment is now 30 days in jail. And because you committed the crime within the last 5 years, in you go, buddy.”

It doesn’t have to be possible for it to be the law. In Calder, the Court interpreted the phrase “ex post facto” to mean criminalization ex post. So you can have civil laws that are ex post but not unconstitutional.


I guess my mistake was in sticking to reality. :slight_smile:

Extremely hypothetical question. Suppose Congress here in 20006 did pass a law saying that as of 1 Jan. 2000, <something or other> was illegal. Obviously, if someone were charged under the law and the matter came to trial the law would be thrown out. But would negating the law require that someone be charged under it? Just exactly how would the law be stricken from the books.