The principle of legality somehow deals with safeguarding the rights of an accused person. It talks about the fact that even if a person is charged with an offence, his life and liberty cannot be taken away without a proper system of codes and rules defined by a legal statute.

One of the maxims which hold the essence of the rule of the Principle of legality is “nullum crimen sine lege, nullum poena sine lege” which means there will be no punishment for an act that has not been defined in the legal statute of the land. This maxim clearly illustrates that a person cannot or should not be subject to criminal punishment unless the act was defined as unlawful before the person committed it.

If the person has committed an act and it is not defined as punishable in any statute of the state then that person is not liable to any punishment.

The same goes with the ‘crime’, the maxim states that an act will not be considered as a ‘crime‘ if it is not defined in the state law.

Purpose of the Principle

The purpose of the rule was to ensure that punishment must be given only on the breach of law which was predetermined by the state or legal society because the rights and liberty of the accused person are in serious and immediate danger.

Nullum crimen sine lege = “no crime without law”

Nullum crimen sine lege = “no punishment without law”

Essential Rules of the maxim:

The Maxim “Nullum crimen sine lege” covers the following essential Rules.

  1. Penal Laws are not retrospectively applicable
  2. Criminal Statutes cannot be extended by Construction.
  3. The Law should be certain and definite.
  4. Penal laws must be accessible.

No ex-facto Penal Laws

It is a simple rule that penal laws are not applied retrospectively. This rule assumes that it would be unjust to state something that was legal at the time when it was done has now become subsequently illegal in the future through a statute.

It means that if an act was done in the past, a person should not or will not be punished for that act under any law that was passed after the act was committed.

Article 20(1): Indian constitution has also provided reasonable sections for the purpose of this essential rule. Article 20(1) states that ‘No person shall be convicted of any offence except for violation of the law in force at the time of the commission of the act charged as an offence, nor be subjected to a penalty greater than that which might have been inflicted under the law in force at the time of the commission of the offence.’

It is clear from the above statement that

  • No Law can make an offence with retrospective operations
  • No Law can subject an accused person to a punishment greater than that which might be inflicted at the time of the offence was committed.

The Supreme Court in Rattan Lal vs State of Punjab AIR 1965 held that: ‘ex-post facto law which is beneficial to the accused is not prohibited by article 20(1) of the Constitution.’

How a Law is considered an ex-post facto Law

  • Criminal Act Done
    • Any law that declares an action unlawful even though it was committed before that law was passed is known as an ex-post facto statute. We can also state that any action that was previously thought to be lawful when it was done is now classified as a criminal act and subject to punishment under new legislation.
  • Harsher Punishment
    • Any law is also deemed ex-post facto if it amends the penalty and imposes a harsher penalty than the one that was attached to the offence when it was committed.
  • Rules of evidence
    • A statute that changes the law’s requirements for admissible evidence and accepts less or different testimony than what was required at the time the offence was committed.
  • Removal of a right or Legal Protection
    • Any law will be considered under the ex-post facto category if it somehow removes or deprives an accused person of any legal right or protection to which they have been entitled.

The Rule of Strict Construct

The rule states that during an accused’s trial, the court must ensure that the act or omission charged as an offence is within the plain meaning of the words used in the provision defining that act or omission as an offence. It must not strain the words used in defining an offence in any way, such as to provide for an omission.

Principle of Casus Omissus: Mean a situation omitted from or not provided for by statute or regulation and therefore governed by the common law.

According to the Strict Construction (interpretation) of penal laws if any substantial element of the statute is omitted in a case then that statute is not applicable to that case. It states clearly that the accused must be given the benefit of the doubt when a statute’s unclear language raises questions regarding its intent and application. This approach is taken because the person accused of the crime faces threat to their life and freedom.

There Should be Certainty in Law

This rule suggests that penal laws should be clear and definite so that people should understand them clearly. This will allow people to better understand their conduct in civilised society must avoid falling into the ambit of these penal laws.

This rule calls for Certainty because it considers legislation to be a prohibition and a prohibition must be clear enough to make people understand that they are not allowed to do certain tasks. It also deals with the generalisation of the terms used in the legislation. It states that legislation should avoid the use of such broad general terms so that the penal law must not bring everybody in the shadow of that law. The terms of the statute should clearly certify the scope of its application.

Penal laws must be accessible.

To allow the application of the principle of natural justice in the legal system penal laws should be made accessible to the public at large. Natural justice demanded that laws be publicised and propagated before they could take effect. It would be against the principle of natural justice if the citizens are penalised by laws of which they had no knowledge.


  1. Rattan Lal vs State of Punjab AIR 1965 SC 444
  2. Hall, Jerome; Principles of the Criminal Law.