The correct option is The principle of natural justice.
Explanation
‘Due Process of Law’ refers to both procedural fairness and substantive reasonableness in the application of law, ensuring that laws and their enforcement are just, fair, and non-arbitrary.
- The principle of natural justice: Correct – It captures the essence of due process by requiring fairness, reasonableness, and adherence to natural justice in both law and procedure.
- The procedure established by law: Incorrect – This denotes mere compliance with legally prescribed procedure, without necessarily examining fairness or reasonableness.
- Fair application of law: Incorrect – This is a partial expression and does not fully encompass the substantive and procedural safeguards inherent in due process.
- Equality before law: Incorrect – This is a separate constitutional principle relating to equal protection, not the concept of due process.
Key Takeaway: Due process ensures that laws and procedures are not only followed but are also fair, just, and aligned with principles of natural justice.