Van Aerssen joined the CDU in 1964, he had been a member of the Kleve district executive of the CDU since 1970 and became a member of the Rhineland regional executive of the CDU in 1973 as Commissioner for European Affairs. As a successor to
Wilhelm Wehren, van Aerssen was a member of the
North Rhine-Westphalian
state parliament from 26 July 1970 to 13 December 1976, where he was chairman of the committee for state planning from 1973 to 1975. From 14 December 1976 to 29 March 1983, he was a member of the German Bundestag for two terms. He was directly elected in 1976 and 1980 in the Kleve constituency. In addition, he was a member of the
European Parliament from 19 January 1977 to 24 July 1989, where he was a member of various committees with a foreign trade orientation. == Literature ==