As per case facts, Respondent No.1, a lecturer with a Ph.D. at recruitment, received four advance increments as per the 1999 UGC Scheme. Later, upon placement as a Selection Grade ... Lecturer, he was denied two additional advance increments, a benefit he believed he was entitled to under the same 1999 scheme. This denial was justified by the University based on a subsequent Government Order from March 2001, which clarified that teachers who already received Ph.D. related increments at recruitment wouldn't get further ones at the selection grade. The High Court sided with the lecturer, stating the 2001 order couldn't apply retrospectively. The University appealed this. The question arose whether the Government Order of March 2001 was a mere clarification of the earlier 1999 order, allowing retrospective application, or a substantive modification, making it prospective. Finally, the Supreme Court dismissed the University's appeal, affirming the High Court's judgment. The Court held that the 2001 order constituted a substantive modification, as it effectively reduced the total advance increments from six to four for lecturers in Respondent No.1's category. Allowing its retrospective application would result in the withdrawal of vested rights, which is impermissible. Therefore, lecturers placed in the selection grade before the March 2001 order are entitled to all incentives stipulated in the December 1999 Government Order.