In the ancient phrase of Gratian, Leges instituuntur cum promulgantur ("Laws are instituted when they are promulgated").
In addition, there were, particularly in the days before satellite communication and cellular phones, persons who could genuinely be ignorant of the law due to distance or isolation.
For example, in a case in British Columbia, four hunters were acquitted of game offenses where the law was changed during the period they were in the wilderness hunting.
[7] Another case, in early English law, involved a seaman on a clipper before the invention of radio who had shot another.
The doctrine, "Ignorance of the law is no excuse", first shows up in the Bible in Leviticus 5:17: "And if any one sin, and do any of the things which Jehovah hath commanded not to be done; though he knew it not, yet is he guilty, and shall bear his iniquity.
"[9] An alternate explanation of the origin of the maxim, though not particularly relevant to the modern context, can be found in the philosophy of the Greeks and Romans.
We find that Cicero wrote the following in De re publica (On the Republic): True law is right reason conformable to nature, universal, unchangeable, eternal, whose commands urge us to duty, and whose prohibitions restrain us from evil.
On the penal side, the quality of the knowledge of the law can affect the evaluation of the animus nocendi or the mens rea, in that certain subjective conditions can weaken personal responsibility.
It was then argued that both the presumed knowledge and the heavily increasing corpus of national legislation were working in favour of lawyers rather than citizens.
This principle is also stated in statutes: In some jurisdictions, there are exceptions to the general rule that ignorance of the law is not a valid defense.
For example, under U.S. Federal criminal tax law, the element of willfulness required by the provisions of the Internal Revenue Code has been ruled by the courts to correspond to a "voluntary, intentional violation of a known legal duty" under which an "actual good faith belief based on a misunderstanding caused by the complexity of the tax law" is a valid legal defense.
It was subsequently ruled in United States v. Freed (1971) that this exception does not apply when a reasonable person would expect their actions to be regulated, such as when possessing narcotics or dangerous weapons.