Dear Stevie,

I hope this link and material will help you

http://connection.ebscohost.com/c/articles/64280942/principle-certainty-criminal-law-lex-certa-case-law-european-court-human-rights

The lex certa principle is breached every day, when two or more judges resolve differently equal cases, under the same legal context. So, the lex certa principle is just a discourse to counterbalance the natural uncertainty of capitalist economy. See the the texts in Max Weber's "Economy and society" about the need of calculus in these economies, it's an excellent description of the material behaviour behind the lex certa principle. Regards

Dear Pramuditha,

Obviously, the law of the land should certain and free from infirmities. It is similarly applicable to the Courts and judges, that's why the principle of Precedent was evolved in common law countries. 

It is well understood concept that the opinion may differ person to person and judges are also human being, so their opinion may differ, but it is the process of settlement of law. Once the Supreme Court of the land pronounce the correct position of law, only than law get settled or get certainty.

Uncertainty in legislation gives free hand to executive to execute the law according to their own interpretation unless it got settled by judicial pronouncement of legislative interventions.

The principle binds the legislature as well as judiciary. In fact judiciary tries to settle the law to make it certain. 

A court (I am writing of the commn law tradition) may take the approach that it has to interpret the law in front of it, but there is a principle that in case of lack of clarity in a criminal statute it should be construed in favour of the accused -- see the Canadian Suprem Court case of R. v. McLaughlin (1980 (attached). 

A court may, especially when faced with a constitutional/human rights challenge to a statute "read it down" -- this is not restricted to vague statutes. Indeed a court would probably prefer to use the interpretation approach rather than reading down because the latter is actually changing the expressed (or maybe the apparent) will of the legislature.

Another approach may be to hold legislation invalid (unconstitutional) because of vagueness. Not that the constitution necessarily expressly say law must be clear, but because the court holds that a human right cannot be limited other than by law that is clear. Especially if the constitution says that a limitation on rights must be "by law".  See the Kenyan case of Coalition for Reform and Democracy v Republic of Kenya (2015) (attached) especially paragraphs 259-263 and 275-76.  

I have limited myself to a very few comments and those on the common law. Of course similar approaches are to be found in other systems and in the European Court. 

I am also attaching a section from an English Court of Appeal case  in 2004 (quoted in a  House of Lords case in 2005) which covers quite a lot of ground.

Within which terms we can say a decision of a Court is "correct"? Indoubtfully not as it would be "true", since the prescriptive speech is out of "truth values", nor as a "discovering of the only correct answer" to a normative problem, because the sole existence of two or more possible answers (given by doctrine, previous decissions of other or the same Court, etc.) reveals that no specific answer is correct in itself. Consequently, the only motive to decide in one way and not in others is the political belief or preference of the Court, understanding "political" widely as a set of representations of the society.

What remains of the "lex certa" principle? It is a rethoric resource, among many others, to justify any decision. The explanation of the use or not use of the principle is not in the principle, which is simply a tool; that principle shall be used (or not used) in any case a Court needs to justify a decision and does not find other argument.

Interestingly, having been an administrative law judge and craved certainty from law and regulation, it was rarely presented for my consideration.  My exposure would include both state (Alabama) and federal ( United States) enactments.  When laws or regulations are developed through the political process, ambiguity is usually the only way such regulation or legislation can survive.  And even in some systems where the law may be clearly stated, a representative of the governing power may ultimately decide whether the decision proposed by the judge is consistent with the goals of the political governing power.  I learned of this in an examination of the People's Republic of China legal system as compared to the one in the United States which relies upon the doctrine of stare decisis in seeking consistency of interpretation.

When the Obamacare law was first enacted and our department of Health and Human Services was attempting to develop the regulations, it presented an interesting situation wherein legal certainty was far from a priority.  The major shift caused by this legislation, which was ultimately upheld by the U.S. Supreme Court, was one which put not only the healthcare industry on its heels, but also every business throughout the country which fell into the requirements of the law.  Moreover, there were provisions within the Affordable Care Act (Obamacare) which eliminated the burden of proving intent in criminal cases brought for violating its provisions.  If that was an attempt to provide certainty, it clearly was not designed to assist the person who mistakenly submitted wrong information to support disbursements there-under and found them defending a serious criminal charge.  In effect the law shifted the burden to the defendant rather than placing it upon the government.

My point is that our law and regulatory scheme in the United States rarely provides enough clarity, especially with the advent of technology changing the environment.  My experience was to remain hopeful for direction in the statute or regulation, but accept that often flexibility was necessary for such regulation to be passed by competing interests.  We have rules of interpretation that we apply to cases, just like the interpretation of contracts which are ambiguous.  However, when a judge discards the clear meaning of terms in a law or regulation, that jurist invites the appeal and reversal of their opinion when such is excessive or unreasonable.

Therefore I must conclude that the system through its operation with checks and balances is ultimately the lex certa , just as much as the actual interpretation of the initial judge examining such rule or law and applying interpretive techniques.  I hope this helps in your consideration of the principle.

I'd add two unconnected points to the collection of very good answers already posted:

This is a perennial problem with international criminal law, where courts often have to spend a lot of time discerning what the existing law is before proceeding with a prosecution.  Nullum crimen sine legem. Legal positivists look for a statute (by treaty, convention, etc.) that somehow binds the defendant and announces what the elements of the crime are. Others are OK relying on "customary law" or even a sense of "natural law"--the idea being that some acts are so heinous, everyone knows or should know they are criminal.

Our clinic recently submitted an amicus brief in a case in our state court based on a theory of omission that raised this principle. The person who sold the victim drugs was convicted for the victim's death by voluntary overdose for failing to return to check up on him or calling for medical help. By statute, in our state criminal liability only extends to "voluntary acts." Voluntary acts is defined to include omissions, but liability based solely on omissions is limited to two situations: when criminal liability for omission is spelled out in the crime's definition, or when a duty to perform the omitted act is  "otherwise imposed by law."  So the theory of this case depended on recognizing the drug seller as being in a "special relationship" with the drug buyer giving rise to a duty to help.  Our brief argued 1) that no such special relationship exists, and in the alternative 2) if it does, that law had not been clearly announced previously, so the defendant did not have fair notice (another way of describing the lex certa principle) that he had a legal duty to return and check up on the victim or call for help (and therefore that breach of that duty can be the basis for criminal liability).