“My oath to support and defend the Constitution, my duty to the people who have chosen me to execute the powers of their great office and not to relinquish them, and my duty to the Chief Magistracy, which I must preserve unimpaired in all its dignity and vigor, compel me to refuse compliance with these demands.”
President Grover Cleveland, Special Message to Congress (Mar 1, 1886). The “demands” involved a congressional request for certain documents.