JUDGMENT :

G. S. Kulkarni, J.

1. This appeal under Section 35G of the Central Excise Act,1944 (for short “CE Act”) arises from an order dated 28 August 2019 passed by the Customs, Excise & Service Tax Appellate Tribunal, Mumbai, Regional Bench (for short “CESTAT”), whereby the respondent’s appeal being Excise Appeal No.525 of 2012 arising out of the order-in-original dated 31January 2012 passed by the Commissioner of Central Excise, Mumbai-II, has been allowed.

2. The appellant / revenue in assailing the judgment of the CESTAT has although raised four questions of law, as fairly agreed by the parties, we confine the adjudication of the present appeal on the following substantial question of law:-

“A. Whether in the facts and circumstances of the case the CSTAT was right in holding that the amendment to Rule 6 of the CENVAT Credit Rules,2004 retrospectively amended by the Finance Act,2010, was applicable in the present case in the light of the provisions of Section 73 of the Finance Act,2010 ?”

3. The controversy in the present appeal revolves around the purport and applicability of Rule 6 of the Cenvat Credit Rules, 2004 (for short ‘CCR, 2004’) under which the duty demand was raised against the respondent. Rule 6 provides for obligation of manufacturer of dutiable and exempted goods and provider of taxable and exempted services. At the outset, it would be necessary to note Rule 6 of the CCR,2004 as it stood prior to its amendment in the year 2008 and post the amendment in the year 2008 which reads thus:-

“Rule 6 prior to 2008 amendment

6. Obligation of a manufacturer of dutiable and exempted goods and provider of taxable and exempted services.

(1) The CENVAT credit shall not be allowed on such quantity of input or input service which is used in the manufacture of exempted goods or exempted services, except in the circumstances mentioned in sub-rule (2):

[Provided that the CENVAT credit on inputs shall not be denied to job worker referred to in rule 12AA of the Central Excise Rules, 2002, on the ground that the said inputs are used in the manufacture of goods cleared without payment of duty under the provisions of that rule.]

(2) Where or manufacturer or provider of output service avails of CENVAT credit in respect of any inputs or input services [***] and manufactures such final products or provides such output service which are chargeable to duty or tax as well as exempted goods or services, then, the manufacturer or provider of output service shall separate accounts for receipt, consumption and inventory of input or input service which is intended for use in the manufacture of dutiable goods or in providing output service on which service tax is payable.

(3) Notwithstanding anything contained in sub-rules (1) and (2) the manufacturer or the provider of output service, opting not to maintain separate accounts, shall follow either of the following conditions, as applicable to him, namely:-

(a) if the exempted goods are-

(i) goods falling within [heading 2207] of the First Schedule to the Excise Tariff Act (hereinafter in this rule referred to as the said First Schedule);

(ii) Low Sulphur Heavy Stock (LSHS) falling within Chapter 27 of the said First Schedule used in the generation of electricity

(iii) Naphtha (RN) falling within Chapter 27 of the said First Schedule used in the manufacture of fertilizer;

(iv) Naphtha (RN) and furnace oil falling within Chapter 27 of the said First Schedule used for generation of electricity;

(v) [newsprint, in rolls, sheets or reels, falling within Chapter 48] of the said First Schedule;

(vi) final products falling within Chapters 50 to 63 of the said First Schedule;

(vii) goods supplied to defence personnel or for defence projects or to the Ministry of Defence for official purposes, under any of the following notifications of the Government of India in the Ministry of Finance (Department of Revenue), namely:-

(1) No. 70/92-Central Excise, dated the 17th June, 1992, G.S.R. 595(E), dated the 17th June, 1992;

(2)