I very strongly disapproved of this presidential action; however I will note that I am satisfied it is perfectly legal. It's not an amendment either; it's part of a lengthy sentence (Article 2, Section 2, Paragraph 1)-- "and he shall have Power to Grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment." (Referring to the President). That paragraph appears to be the 'misc' box of Presidential Powers put in by the framers-- its preceding clause is the rather eccentric "he may require the Opinion, in writing, of the principal Officer in each of the executive Departments, upon any subject relating to the Duties of their respective Offices," which seems a touch dull and passé.