Is there any concept in the legal world that covers laws that are too difficult or impractical to comply with?

Here's an example; suppose an American moves to the UK and buys a house. The mortgage is for £300,000, which is equivalent to $300,000 at the time of purchase. However by the time the house is sold, 20 years later, the house is worth £900,000 and is equivalent to $1,200,000. The owner must now calculate exactly how much money he earned - taking into account the GBP/USD exchange rate every time there was a mortgage payment. This would require many dozens or possibly hundreds of hours to do, at massive cost (if performed by a tax professional).

In the example above, should the owner not properly follow these rules, and perhaps just make some rough estimate, could he be held criminally responsible for filing an incorrect tax return?

Or does there exist some kind of defense that complying with the law would simply have been completely unreasonable or impractical?

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    I get that the example is hypothetical, but I don't think it reflects how US tax law actually works. When the owner sells the house, he simply owes capital gains tax on his gain - the difference between the purchase price and sale price, each in dollars as of their respective dates. That calculation takes about 1 minute. The mortgage payments are only relevant if he wishes to deduct the mortgage interest from his income - but he would have had to be doing that each year, not all at once at the end. Commented Mar 28, 2019 at 18:21
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    And for that, he has only to review his mortgage statements, determine the amount of each payment that was allocated to interest, and convert it to dollars. Doing that for 12 payments would be a matter of a few minutes, especially when historical exchange rates can readily be found online. Even if you had to do 20 years' worth, it would be a matter of maybe an hour or two, not "dozens or hundreds of hours", unless our taxpayer is remarkably inept. Commented Mar 28, 2019 at 18:23
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    Nate Eldredge - you are right, but with one (important) exception: assuming the borrower is cash basis, the interest on the mortgage is converted @spot, but the principal payment can create forex gain or loss based on the difference between the spot and mortgage issue date rates. A little too complicated to get into in a comment... Commented Mar 28, 2019 at 19:26

3 Answers 3


Sometimes laws contain exceptions when they are "unreasonably" burdensome. For example the US "Americans with Disabilities Act" does not require providing wheelchair access when this would require tearing down a building, or even major structural changes, and only requires that employers provide "reasonable" accommodations.

But the clerical cost of compliance is not usually a reason for an exception.

In the case in the question, since the owner does not actually make a profit until the house is sold. it might be sufficient to compute the profit in local currency, and then apply the conversion factor once to the total profit. But even if a separate conversion had to be applied to each separate payment, that is exactly the kind of thing that an app or computer program could do quickly and easily. Nothing says that the computation need be manual.

When compliance with a law is impossible or would violate some other law, courts generally hold that the law cannot be enforced, or must be complied with in some alternate way.



You cannot be punished for failing to comply with an impossible law but impracticable, difficult, time-consuming or expensive do not amount to impossible.

If the law makes your operations uneconomical then you can either comply with the law and incur a loss, withdraw from the market, or operate as a criminal enterprise.

There are many examples through history of businesses and entire industries effectively impacted by the cost of compliance. For example, chemical companies face much higher costs now then when they could freely dump toxic waste in residential areas.


The term "mens rea" is used in criminal law in reference to whether the accused had intent. There are similar burdens in most states in civil cases as well.

This site provides a good overview of how it is applied. https://www.dwlawtx.com/issue-intent-civil-litigation/

They don't usually look at reason if you define reason as common sense, but judges do look at whether you intended to commit the offense or did something that was reckless. Most of the time, people will try to understand if an accident occurs.

  • This doesn't really respond to the question. The OP is not asking what happens if s/he makes a mistake, s/he says that the law is burdensome to comply with, and asks if compliance can be avoided for this reason. Also the question is not limited to US jurisdictions. mens rea is required for many but not all criminal prosecutions. Many civil statutes impose strict liability, where intent is not relevant. Commented Mar 29, 2019 at 0:15
  • @DavidSiegel There is not a burdensome law. You are splitting hairs there that no judge would under the "reasonable person" view of the law. Again, I am from Illinois, not everywhere else, but I have never seen a civil law that did not require intent or negligence.
    – Putvi
    Commented Mar 29, 2019 at 17:15
  • The OP claimed it was burdensome, although i think incorrectly. The federal superfund law, for example, imposes strict civil liability, even retroactively, with no element of intent. Copyright infringement is another case where there can be liability without intent. But my main point is that you are answering a question that was not asked, and not answering the one that was. Commented Mar 29, 2019 at 17:42
  • I see what you are saying, but those civil laws that don't mention intent or say intent is not needed are adding that so a judge can decide you were negligent. I get that he is saying burdensome and not intent, but the only case law regarding something like that would fall under intent or negligence. It wouldn't make sense to ignore all that hundreds of years of case law bc he said burdensome, any reasonable person can see it should be called intent or negligence in court.
    – Putvi
    Commented Mar 29, 2019 at 17:45
  • I am sorry, but in the superfund cases liability has been imposed when the defendant did not even know, nor could have known, that a violation was occurring or had occurred. It has been imposed on purchasers of sites contaminated by other entities, before the law was even passed, so no one could have known it was against the law, because it wasn't, then. No negligence, no intent, but still liability. That is what "STRICT LIABILITY" means. Commented Mar 29, 2019 at 17:50

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