liggio was a trustee with the competitive enterprise institute since 1994 and the institute for economic studies-europe in aix-en-provence since 1999. from 1988 to 1998, he had been a trustee of the philadelphia society, of which he was president from 1992 to 1993 and from 1994 to 1995. he had been also a trustee with the institute for humane studies-europe in paris from 1989 to 1999 and of the acton institute for the study of religion and liberty from 1990 to 1999. he also served on the boards of a number of other think tanks: