He returned to Columbia as a visiting professor in 1957 and then joined the permanent faculty, becoming the youngest full professor in the University's history in 1960. He has mediated for New York City in transit worker contract negotiations, as well as firefighter and police disputes. From 1962 to 1966, he was the Research Director concerning Legal Restraints on Racial Discrimination in Employment for the Twentieth Century Fund. He was a law consultant for "Time" magazine for fifteen years (1965–1980). Sovern served as Special Counsel to Governor Brendan Thomas Byrne of New Jersey from 1974 to 1977. He was the co-chairman of the Second Circuit commission on Reduction of Burdens and Costs in Civil Litigation from 1977 to 1980, chairman of the New York City Charter Revision Commission from 1982 to 1983 and chairman of the State-City Commission on Integrity in Government in 1986.