ITC Disallowed Under 16(4) - Goods and Services Tax - GST

My client filed GSTR-3B for January 2019 on 30.09.2020 because his GST registration was cancelled from 31.12.2018 to 16.09.2020. The client filed the return under the GST amnesty scheme, where the late fees were restricted to Rs. 500/- if the return was filed by 30.09.2020. However, the client received a demand order from GST authorities under section 73 of the CGST Act, 2017 to reverse the ITC availed under section 16 (4) as the return was filed after the due date mentioned in section 39 . In March 2023, another amnesty scheme was introduced, allowing GST registration to be revoked after fulfilling certain conditions. Additionally, there was a judgment from the Gujarat High Court ( Allyssum Infra vs Union of India - 2023 (4) TMI 1123 - GUJARAT HIGH COURT ) , where the taxpayer's registration was revoked after a long period under the said amnesty scheme, and ITC was allowed even though the return was filed after the due date. What are the points on which I can argue and appeal for a favorable order?