 He also found time to return to his alma mater, UST, where he briefly served as dean of its Faculty of Civil Law.After the toppling of Marcos from power, Concepción was appointed as one of the commissioners tasked to draft the 1987 Philippine Constitution.As one of its members, he is responsible for crafting the contents regarding civil liberties, as well as an added provision in the Executive Powers of the President, a clause limiting the effects of martial law with respect to the writ of habeas corpus, based on one of the decided cases of the Supreme Court in which he wrote.