The rationale of the doctrine is that if ignorance were an excuse, a person charged with
criminal offenses or a subject of a civil
lawsuit would merely claim that one was unaware of the law in question to avoid liability, even if that person really does know what the law in question is. Thus, the law
imputes knowledge of all laws to all persons within the
jurisdiction no matter how transiently. Although it would be impossible, even for someone with substantial legal training, to be aware of every law in operation in every aspect of a
state's activities, this is the price paid to ensure that
willful blindness cannot become the basis of
exculpation. Thus, it is well settled that persons engaged in any undertakings outside what is common for a normal person will make themselves aware of the laws necessary to engage in that undertaking. If they do not, they cannot complain if they incur liability. The doctrine assumes that the law in question has been properly promulgated—published and distributed, for example, by being printed in a
government gazette, made available over the
Internet, or printed in volumes available for sale to the public at affordable prices. In the ancient phrase of
Gratian,
Leges instituuntur cum promulgantur ('
Laws are instituted when they are promulgated'). For a law to obtain the binding force which is proper to a law, it must be applied to the men who have to be ruled by it. Such application is made by their being given notice by promulgation. A law can bind only when it is reasonably possible for those to whom it applies to acquire knowledge of it in order to observe it, even if actual knowledge of the law is absent for a particular individual. A secret law is no law at all. In
criminal law, although ignorance may not clear a defendant of
guilt, it can be a consideration in
sentencing, particularly where the law is unclear or the defendant sought advice from law enforcement or regulatory officials. For example, in one
Canadian case, a person was charged with being in possession of
gambling devices after they had been advised by
customs officials that it was legal to import such devices into Canada. Although the defendant was convicted, the sentence was an
absolute discharge. 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. Another case, in early
English law, involved a seaman on a
clipper before the
invention of radio who had shot another. Although he was found guilty, he was pardoned, as the law had been changed while he was at sea. Although ignorance of the law, like other
mistakes of law, is not a defence, a
mistake of fact may well be, depending on the circumstances: that is, the false but sincerely held belief in a factual state of affairs which, had it been the case, would have made the conduct innocent in law.
Presumed knowledge of the law is the principle in
jurisprudence that one is bound by a law even if one does not know of it. The concept comes from
Roman law, and is expressed in the
brocard ignorantia legis non excusat. The essential public character of a law requires that the law, once properly promulgated, must apply to anyone in the
jurisdiction where the law applies. Thus, no one can justify their conduct on the grounds that they were not aware of the law. Generally, a convention exists by which the laws are issued and rendered accessible by methods, authors and means that are simple and well known: the law is readable in certain places (some systems prescribe that a collection of the laws is copied in every local city council), is made by certain authorities (usually sovereign, government, parliament, and derivative bodies), and enters into effect in certain ways (many systems for instance prescribe a certain number of days—often 15—after issue). This is commonly intended as a
constitutional regulation, and in fact many
constitutions or
statutes exactly describe the correct procedures. However, some recent interpretations weaken this concept. Particularly in
civil law, regard can be had to the difficulty of being informed of the existence of a law considering the lifestyle of the average citizen. On the penal side, the quality of the knowledge of the law can affect the evaluation of the or the , in that certain subjective conditions can weaken personal responsibility. The theme was widely discussed, also for political reasons, at the time of
the Enlightenment and in the 18th century, given the heavy proportion of illiterate citizens in European countries (who would have some difficulties being aware of all the laws in a country). 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. In recent times, some authors have considered this concept as an extension of (or at least as analogous to) the other ancient concept (typical of
criminal law) that no one can be punished under a law that was issued after the action was committed (non-retroactivity of the law. See
ex post facto). This interpretation is however disputed, given that the matter would hierarchically more properly refer to a constitutional doctrine rather than to a civil or penal one. Some modern criminal statutes contain language such as stipulating that the act must be done "knowingly and wittingly" or "with unlawful intent", or some similar language. However, this does not refer to ignorance of laws, but having
criminal intent. ==History==