Is "the law is impossible to follow" a valid defense?

Can you form a defense based on the fact a given law is physically and/or logically impossible to obey?

I suppose an example would be having a 45 mph speed limit immediately followed by a 15 mph speed limit, with insufficient space to decelerate and minimum speed laws in effect (such that it is a violation to do more than, say, five mph under the limit). But that’s just an example; if another example would serve better, use it, instead. I suppose a more realistic example would be an extremely convoluted scenario arising from the interaction of multiple laws all drafted separately.

(I can only imagine this has come up at some point, if only as a failed argument.)

There is such a defense in US criminal law – see the Wikipedia article on Necessity, which links to articles on the topic in Canadian and English criminal law. It seems to be rarely used successfully, but may be an element in prosecutors deciding not to charge some possible users of the defense.

Fixed link and that doesn’t sound quite right:

In my example, you’re caught between two horns, in that you can either go under the minimum limit in the 45 mph zone in order to not exceed the limit in the 15 mph zone, or you can exceed the limit in the 15 mph zone in order to not go under the minimum limit in the 45 mph zone. So, whichever you did, it wasn’t necessary as you could have done the other.

Also, there is no implication that you were morally required to break the law. You were physically required, but that doesn’t seem to be what necessity covers. No greater harm was prevented by your violation.

And as an anecdote, I used that very defense in convincing the local prosecutor to drop the charges against me for having insufficient life jackets aboard my boat when I had originally taken two loads of passengers to a remote location, but when the boat started back, it was barely sputtering and a storm was approaching. No cell service, no roads, lightning coming.

So I loaded everyone on board, was cited by the lake patrol for insufficient number of life jackets to passengers and challenged the ticket on those two bases. The prosecutor thought I was 100% right and refused to prosecute.

For your situation, I would go with “substantive due process.” You weren’t really given due process of law if you HAD to break the law no matter what you did.

This situation has come up in local parking regulations where a *clear and convincing *standard was required. It’s not about crimes, but if two signs contradict on whether parking is allowed, it’s allowed. You have to go court to challenge it, with pictures of the signs, and you still end up paying the court costs, which is pretty much what they’re after anyway.

My first thought was the famous example (is it true, or is it an UL?) “When two trains meet each other at a railroad crossing, each shall come to a full stop, and neither shall proceed until the other has gone.”

Now, yeah, this is actually possible to obey: neither train ever moves again. But in practice, it is impossible to follow, and I really, really doubt anyone would get prosecuted under it. Any sane judge would throw the case out.

I have seen photographs of signs with the OP’s exact situation, so it does exist. Now, I suspect that where the speed limit signs violate the Intermediate Value Theorem, it’s just politely ignored, with one or both of the limits going unenforced: No cop is going to ticket you for going under the minimum if you’re accelerating up to the limit in a reasonable span before or after the change.

I realize the example in the OP is just an example and not the crux of the issue, but I’ve always assumed it’s universally understood, in the case of speed limit signs, that drivers will be looking ahead to see signs and adjusting their speed up or down as they pass from one zone into the other. I’d be surprised if anyone tried to prosecute under that circumstance.

Courts do not usually expect a person to do something which is impossible to do so. Note impossible to do so, not merely difficult.

There should be Speed Zone signs that inform drivers of sudden changes. Obviously there aren’t in every case, if would make speed traps less effective. And they will prosecute under any circumstance, because it’s not a crime, it’s a traffic violation, and that’s a big money maker. If there were two different speed limits posted you’ll easily get off the charge, but if you exceed a clearly marked speed limt, even if it’s a trap, you don’t really have a defense.

Jearl Walker was (or is) a professor at Cleveland State University and used to come on to the Canadian science program Quirks and Quarks. One day, he told the following story. He got red light violation ticket driving down Euclid Ave (one of the main thoroughfares of Cleveland). He challenged the ticket and won. He showed that given normal reflexives, normal stopping distance, and the shortness of the yellow light, it was impossible for a car traveling at the speed limit to come to a stop before the intersection.

While there is a doctrine in criminal law of factual or legal impossibility of performance, they would not apply here.

Two theories come to mind of a defense.

  1. Due Process (as was mentioned). What is DP? Well, simply, it is the Process a person is Due when the govt. wishes to deprive them of thier 14th AM right.
    The DP Clause mandates a NOTICE REQUIREMENT in your example, so that a motorist has an ample opportunity to COMPLY with the law. Having non breaking speed limits which do not afford a person time to Comply deprives them of DP, IMO.

If you pulled up to a parking meter and a cop gave you a ticket right away for an expired meter, he has not complied with DP as you MUST be given a reasonable time to exit and deposit.

Here is a similar example from memory of an Ohio case. While it deals with weight limits, the substantial ruling is a NOTICE REQUIREMENT is mandated when laws conflict.

As a more direct example, Ohio permits a right turn on red, but a Municipality can forbid such, but they MUST post a sign noting it, the NOTICE of Process. While the old adage is “One is presumed to know the law”, does this mean a traveler needs to know the Ordinances in every town they pass through so they do not make an illegal right turn on red. The SC says NO!
…Thus, while a municipality has the power to regulate
traffic within its jurisdiction, if local traffic regulations
are at variance with provisions of state law, they do not
become effective “until signs giving notice of the local
traffic regulations are posted * * *.” R.C. 4511.07. This is
a notice requirement and its purpose is clear. While the
municipality may legislate in this area, it must post signs to
give warning of a variant local regulation to drivers so that
they may not unwittingly violate the law…

2. The 4th AM.

It states in part, that there must be NO UNreasonable seizures. To cite/arrest a person for violating a speed limit sign with no time to comply, IMO is an UNreasonable seizure.