Why couldn’t UPA nail down Modi in 10 years of its rule? The answer lies in Commissions of enquiry act precluding central government from appointment another commission for the same purpose.
People often ask, UPA was in power in centre for 10 years during 2004-2014. If Modi was really culpable in the 2002 genocide in Gujarat, how come the centre could not do anything against him?
The answer lies in the legal provisions of the commission of enquiries act of 1952 that prevents a state or central government to create another commission of enquiry for a matter already being handled by an existing commission. To be exact, section 3 of the act says: 
Provided that where any such Commission has been appointed to inquire into any matter by a State Government, the Central Government shall not appoint another Commission to inquire into the same matter for so long as the Commission appointed by the State Government is functioning, unless the Central Government is of opinion that the scope of the inquiry should be extended to two or more States.
Imagine you are Narendra Modi. After the massive riots in Gujarat, the heat is on you. Even the PM, from your own party, is hinting at you not doing your “Raj Dharma”. You are accused of being complicit in abetting violence. What do you do?
Easy – appoint a judicial commission of enquiry. These can only recommend action, but not actually take any action, and cannot punish anyone.
On 6 March 2002, the government of Gujarat appointed a commission of inquiry under section 3 of the Commissions of Inquiry Act, 1952 to investigate into the Godhra train burning incident, the subsequent riots and the adequacy or lack thereof of the administrative measures taken to prevent and deal with the disturbances that followed, both in Godhra and subsequently across the state.  The Commission was a single member commission consisting of Justice K. G. Shah, a retired Gujarat High Court judge. It was given three months time to submit its report.
Shah Commission: Terms of Reference (2002)
- To inquire into –
- The facts, circumstances and the course of events of the incidents that led to setting on fire of some coaches of the Sabarmati Express train on February 27, 2002 near Godhra railway station.
- The facts, circumstances and course of events of the subsequent incidents of violence in the State in the aftermath of the Godhra incident.
- The adequacy of administrative measures taken to prevent and deal with the disturbances in Godhra and subsequent disturbances in the State.
- To ascertain as to whether the incident at Godhra was pre-planned and whether information was available with the agencies, which could have been used to prevent the incident.
- To recommend suitable measures to prevent recurrence of such incidents in future.
It is clear that the terms of reference (TOR) of the Shah Commission attaches less importance to the serious incidents in Ahmedabad and elsewhere as compared to its concern over what happened in Godhra. While the element of pre-planning, if any, behind the Godhra incidents is to be looked into, the need to adopt a similar approach in regard to the incidents in Ahmedabad and elsewhere, is conspicuously ignored.
Further, Justice K.G. Shah, had close ties to the BJP and a history of anti-minority judgements. One of his judgements on an issue concerning Muslims was overturned by the Supreme Court of India with a comment that raised doubts on his ability and impartiality. The apex court had said that the
“finding of the judge is not based on appreciation of evidence, but on imagination”.
Shah’s alleged closeness to Narendra Modi provoked outrage from the families of the victims as well as from Human Rights organisations, and resulted in call for a more independent head for the commission. As a result, on May 21, 2002, the government of Gujarat reconstituted the Commission into a two-member committee, and appointed retired Supreme Court judge G. T. Nanavati as chairman, which thus became known as the “Nanavati-Shah Commission.”
“Within a short time the Government of Gujarat found it necessary to reconstitute the Commission in public interest, by converting the single member Commission into two members Commission headed by a retired Judge of the Supreme Court of India. Therefore, the Government by a Notification dated 21st May, 2002 appointed one of us (Mr. Justice G.T. Nnavati,) as a member and chairman of the Commission. On 3-6-2002 the Government amended the 6th March notification and included within the scope of inquiry the incidents of violence that had taken place in Gujarat till 30th March, 2002.” [SIC]
Shah died on 22 March 2008, just a few months before the commission was due to submit its interim report, and on 5 April 2008 the Gujarat High Court then appointed its retired judge Akshay H. Mehta to the committee on 6 April 2008. This was opposed by the activists, as Akshay Mehta was the same judge who had granted bail to Babu Bajrangi in Naroda case. 
Commission is hence variously also known as the Shah-Nanavati Commission or the Nanavati-Shah-Mehta Commission.
The credibility of the Commission’s report was called into question when the investigative magazine Tehelka released a video recording showing Arvind Pandya, counsel for the Gujarat government, discussing the Commission. In the video, Pandya states that “Hindu leaders” need not concern themselves about the findings of the Shah-Nanavati commission; since Shah was “their man” and Nanavati could be bribed, the findings would definitely be in the BJP’s favour.
TEHELKA: So is Nanavati absolutely against you people?
Pandya: Nanavati is a clever man…He wants money… Of the two judges, KG Shah is intelligent… woh apne wala hai [he is our man]… he is sympathetic to us… Nanavati is after money…
2004 – changes to Terms of Reference
In May 2004, UPA caused a surprise upset in the Lok Sabha elections. On 14th of Jul, 2004, the new Railway minister announced a fresh probe into the Godhra incident.  This was vehemently opposed by the BJP. A few days later, on 20 July 2004, the Gujarat government modified the terms of reference of the Nanavati commission.
..on 20-7- 2004, the Government amended that notification of 6th March and widened the scope of inquiry.
The following two clauses were added :
(d) Role and conduct of the then Chief Minister and/or any other Minister(s) in his council of Ministers, Police Officers, other individuals and organizations in both the events referred to in clauses (a) and (b);
(e) Role and conduct of the then Chief Minister and/or any other Minister(s) in his Council of Ministers, Police Officers (i) in dealing with any political or non-political organization which may be found to have been involved in any of the events referred to hereinabove; (ii) in the matter of providing protection, relief and rehabilitation to the victims of communal riots (iii)in the matter of recommendations and directions given by National Human Rights Commission from time to time.” By that notification the Government also included within the scope of inquiry the incidents of violence that had taken place till 31-5-2002.
Clearly, this was a hogwash, aimed at preventing the centre towards forming another commission of inquiry on the grounds of any missing elements within the terms of reference. Note that the Nanavati commission took 12 years, and while its interim report was tabled in Sep 2008, it took another six years, before it submitted its final report only  after the BJP government came to power in the centre, on 18 Nov 2014. This, again, looks like a deliberate ploy to prevent the centre from appointing another commission.  
The deposition of B Sreekumar, symptoms of fact fudging
One of the good things about Nanavati Commission was that it held hearings in public. However, there is one revealing and curious exception to this.
In August 2011, new allegations surfaced about Mr Modi bribing the lawyers of Mallika Sarabhai, a noted Social activist and danseuse based in Ahmedabad, and a vocal critic of Mr Modi. The Nanavati commission wrote to B Sreekumar saying that if he had anything to say on Bhatt’s allegation about Sarabhai’s PIL, he ‘may’ file an affidavit before it. When Sreekumar responded with the affidavit on 15 September 2011, he found himself in the witness box within a fortnight before an evidently disturbed commission.
Though it was the eighth affidavit he had filed before the commission, this was the first time he had been summoned since his oral deposition seven years earlier on the first affidavit.
The special hearing on 30 September 2011 was, however, not due to any concern on the part of the commission to question Sreekumar about Modi’s alleged subversion of the judicial process. Instead, as the commission’s records show, it ‘sought certain clarifications’from Sreekumar, in a bid to make him change one innocuous word in his affidavit and its covering letter.
Nanavati made no bones about his worry that on this matter damaging to Modi, Sreekumar had put on record that he had been ‘directed’ by the commission to respond. Nanavati was exercised over the word ‘directed’ as Sreekumar, to his mind, had merely been given him an option to respond by saying that he ‘may’file an affidavit. Clearly, Nanavati was anxious to set the record straight lest Modi got the impression that the commission had been overly interested in finding out whether he had interfered with the Supreme Court’s functioning. At the same time, Nanavati was hobbled by the need to carry out the correction discreetly, in keeping with the dignity of his office. So, in a departure from its own norm, the commission held the hearing in camera.
The manner in which the commission recorded its exchange with Sreekumar, gave away the underlying purpose of fact-fudging.
Q. In your letter forwarding your affidavit you have stated ‘as directed by the Commission in its letter No . . ., I hereby submit my eighth affidavit’and we put it to you that the commission has not directed to you by the said letter to file affidavit. (He is shown letter dated 3.8.2011.)
A. I construed the word ‘may’ used in that letter as a direction and therefore, I have stated so in my letter dated 15.9.2011.
Q. The Commission makes it clear to you that there is no direction from the Commission to you to file any affidavit in connection with the issue raised by Ms Mallika Sarabhai and Shri Sanjiv Bhatt. Therefore, will you like to delete the words ‘as directed’ from your letter dated 15.9.2011 and the words to that effect in paragraph 3 of your affidavit?
A. I do not want to delete those words either from my letter or from my affidavit.
Q. We again put it to you that it would be incorrect to say that you were directed by the Commission to file an affidavit in view of the clear language used by the Commission in its letter dated 3.8.2011?
A. As I understood that the Commission wanted to know the data and inputs regarding Ms Mallika Sarabhai’s PIL, I took it as an instruction to be complied with by me. In my view, the relevant matter in my eighth affidavit has direct connection with the terms of reference made by the Government of Gujarat to the Hon’ble Commission.
Much to the commission’s disappointment, Sreekumar did not yield to its repeated pleas to read ‘may’ as an option rather than a ‘direction’. How did things come to such a pass that a former Supreme Court judge was reduced to making such requests to a witness while conducting a commission of inquiry? What facts could Nanavati be trusted to find when he seemed so anxious to be on the right side of Modi, the main subject of his inquiry?
In light of this timidity displayed by Justice Nanavati, it should come as no surprise that despite the change in the terms of reference to include the role of the Chief Minister, the Nanavati commission felt no need to ever question Mr Modi. 
It toed the Gujarat Government’s line on Godhra being a pre-planned terrorist conspiracy. However, this was contradicted by the Gujarat HC.  While the Nanavati Commission indicted Maulavi Umerji as the mastermind of the conspiracy in Godhra, the trial court acquitted Umerji and many others whom Nanavati commission had found guilty.  So, whatever “evidence” a retired judge of the honourable Supreme Court of India had found against these, could not even stand the scrutiny of a trial court.
On 18 November 2014, after the BJP government had come to power in the centre, the long running charade and hogwash, otherwise known as the Nanavati-Mehta commission finally came to an end.