"...he shall take Care that the Laws be faithfully executed...."
--U.S.Constitution, Article II, Section 3, concerning the obligations of the President
"No person shall be...deprived of life, liberty, or property, without due process of law...."
--U.S. Constitution, Amendment V, part of the Laws which the President is to ensure are faithfully executed
"'I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.'"
--U.S. Constitution, Article II, Section 1, containing the words of the oath which the President takes upon entering office