He also served as Rector Magnificus of the Vrije Universiteit Amsterdam, taking office on 1 January 1976.

After the election of 1977 De Ruiter was appointed as Minister of Justice in the Cabinet Van Agt–Wiegel, taking office on 19 December 1977.

After the election of 1982 De Ruiter returned as a Member of the House of Representatives, taking office on 16 September 1982.

In January 196 De Ruiter announced his retirement from national politics and that he would not stand for the election of 1986.

De Ruiter retired from active politics and returned to the public sector and was appointed as Attorney General of the Courts of Appeal of Amsterdam, serving from 1 September 1986 until 1 January 1991.