It's the clause that prevents rogue judges from lording it over the president and erasing his Constitutional powers.

• "Article II of the Constitution provides: “The executive Power shall be vested in a President of the United States of America.” The oath derives from the plain text of Article II to “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.” The only limits on that executive power concern treaties, principal office nominees, and “inferior Officers” whom Congress chooses “by law” to vest the appointment power in. At all times, he “shall take care that the laws be faithfully executed.” The take care clause requires Presidential control of the executive branch and all its personnel, unless expressly removed “by law” by Congress for “inferior officers.” As the Supreme Court surmised: “The entire executive power belongs to the President alone.”

Robert Barnes