In 2012, the Manmohan Singh government appointed Luthra to the post of the Additional Solicitor General (ASG). One of the biggest cases in his tenure as ASG was the proposed release of the seven convicts in the Rajiv Gandhi assassination case. The Tamil Nadu government had proposed to remit the sentence of life for the seven convicted for the assassination of Rajiv Gandhi release them after their death penalty was commuted to sentence of life by the Supreme Court in 2014. The then Attorney General of India, late senior advocate Goolam Essaji Vahanvati, the then Solicitor General senior advocate Mohan Parasaran and Luthra swiftly moved a writ petition to the Supreme Court on behalf of the Union Government challenging the power of the Tamil Nadu government to remit the sentences of the convicted Sriharan alias Murugan and six others. The remittance was put on hold by the Supreme Court which in a later sentence in December 2015, held that a state government has no suo motu power to remit sentences of persons who were convicted under a central Law and cases investigated by the CBI.