The expression 'Personal Liberty' in Article 21 has broad scope, encompassing various rights that constitute an individual's personal liberty. Some of these rights have been elevated to the status of distinct fundamental rights and receive additional protection under Article 19. When interpreting provisions conferring fundamental rights, the court's aim should be to expand their reach rather than diminish their meaning through judicial construction. Article 21 ensures that no person shall be deprived of their life or personal liberty except in accordance with a reasonable, just, and fair procedure established by law.

Compliance with natural justice is implicit in Article 21. If any penal law (such as the Passport Act) does not specify hearing requirements before affecting an individual, the court implies those requirements to ensure a reasonable and non-arbitrary procedure. Article 21 is intertwined with Article 19, and even when there is no infringement of fundamental rights under Article 21, a law that abridges or takes away rights under Article 19 must meet the challenges of Article 19 and the hypothesis of Article 14.

The interaction of Articles 14, 19, and 21 emphasizes reasonableness, which runs like a golden thread through the fabric of fundamental rights. The concept of due process of law, synonymous with 'procedure established by law' in the American Constitution, was rejected by the Supreme Court. Article 21 protects personal liberty against executive interference unsupported by law, where 'law' refers to enacted law or state law.

A procedure that is unreasonable cannot conform to Article 14, as reasonableness permeates the entire article. The principle of natural justice demands that the person concerned must have a reasonable opportunity to present their case before being affected by penal law.