Exhibit 1.1 VAN KAMPEN UNIT TRUSTS, SERIES 789 TRUST AGREEMENT Dated: September 2, 2008 This Trust Agreement among Van Kampen Funds Inc., as Depositor, The Bank of New York Mellon, as Trustee and Van Kampen Asset Management, as Supervisor, sets forth...Trust Agreement • September 2nd, 2008 • Van Kampen Unit Trusts Series 789
