The phrases “Due Process of law” and “procedure established by law” prima facie appear to have similar meanings but a closer inspection reveals how this could not be farther from the truth.
The former evolved from Section 39 of the Magna Carta which stated “for depriving an individual of their personal liberty, per legem terre (law of the land) had to be abided”
In modern understanding Rule of law is broadly understood to encompass four fundamental principles-
First, that a fair trial must be given; second, the court or agency which takes jurisdiction in the case must be duly authorized by law to such prerogative; third that the defendant must be allowed an opportunity to present his side of the case; and fourth that certain assistance including counsel and the confronting of witnesses must be extended.
On the other hand for a law to come under the ambit of “procedure established by law” it solely has to confirm to the process of law making. In Indian context this entails being passed in a democratically elected parliament, getting presidential assent and finally the notification of the law.
Which of the two concepts a country follows has a direct bearing on the scope of judicial review “procedure established by law” empowers the court to repudiate laws only if they are ultra vires of the constitution.
While in due process the court has powers to consider whether the legislation is a “good law”  or not, hence the scope for subjective satisfaction of the judges increases manifolds.
This can be best illustrated through the celebrated case of Maneka Gandhi vs. Union of India.
The petitioner Maneka Gandhi argued that impounding a person’s passport under section 10(3)c of Passport of India Act, 1967 in “public interest”  was unjust and volative of right to equality and right to personal liberty since it did not accord the right to be heard to the aggrieved.
It was here that the court adopted the  concept of due process and held that laws made under article 21 should be fair, just and reasonable and thus stuck down the provision despite adhering to the “procedure established by law” as envisaged in the Constitution.

This concept  went on to become an intrinsic part of the Indian jurisprudence so much so that in Sunil Batra v. Delhi Administration (1979) Justice Krishna Iyer observed that Article 21 is counterpart of procedural due process of USA. Justice K.G. Balakrishnan along similar lines held substantive due process as a “guarantee” under the Indian constitution

At this juncture the reader might wonder why erudite framers of the Indian Constitution did not incorporate such a noble concept in our Constitution. Honourable B.R. Ambedkar, who was a vociferous advocate for the concept of “due process” best described the dilemma of the constituent assembly as “sailing between Charybdis and Scylla” since it was a question of according more power to either the parliament, which could make erroneous legislations motivated by political passions or to a handful judges in the Supreme Court who would have their own political and ideological biases being empowered to decide whether a legislation is a “good law” or not.
The court decided not to bestow this power on the judges opined that courts are not as sensitive to public needs in social and economic sphere as politicians who’re answerable to the people in order to garner votes.

But in the post Maneka Gandhi world we have witnessed that this presumption of the constitutent assemble was largely fallacious and adoption of the due process has led to  liberalization of bail procedures, restricting the solitary confinement, speedy disposal of criminal trials, strict procedure for arrest of person, liberalizing the rule of locus standi, ensured the legal assistance to the needy people, and awarding death sentences in rarest of rare case.     

In fact, the detention of political rivals with mala fide intent of quelling legitimate  political dissent during the Emergency under Indira Gandhi could have been avoided, averting a great national tragedy had the Supreme Court adopted the concept like the numerous High Courts did.

With the given backdrop Supreme Courts virtual surrender of the power of judicial review in recent times is baffling perhaps even concerning. In Rajbala vs Harayana (2015) a two judge bench of the SC rejected the doctrine of substantive due process in India, the author finds it  pertinent to mention here that it is owing to this substantive due process that we have fundamental rights unenumerated in the constitution like  Right to privacy which is in vogue because of the security concerns from the Arogya Setu app.
Here, the remarks of the Chief Justice of India  in an interview published in The Hindu are extremely telling wherin he said “this is not a situation where declaration of rights has much priority or as much importance as in other times”
This eerily resonates with the majority judgement in the ADM Jabalpur case which subsequently led to gross human rights violation during the emergency. In a constitutional republic like ours, the means are as important as the end. It is during such emergencies that the mighty court of law, defender of the public rights is expected to lead from the front and set an example not only for the lower courts but also for other branches of the government which hopefully the Indian Supreme Court will soon do.