Article II, Section 2, Clause 1:
The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States; 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, and he shall have Power to grant Reprieves and Pardons for Offences against the United States, except in Cases of Impeachment.
The Constitution establishes the President’s authority to grant clemency, encompassing not only pardons of individuals but several other forms of relief from criminal punishment as well. The power, which has historical roots in early English law, has been recognized by the Supreme Court as quite broad.
In the 1886 case Ex parte Garland, the Court referred to the President’s authority to pardon as unlimited except in cases of impeachment, extending to every offence known to the law and able to be exercised either before legal proceedings are taken, or during their pendency, or after conviction and judgment.
Much later, the Court wrote that the broad power conferred in the Constitution gives the President plenary authority to ‘forgive’ [a] convicted person in part or entirely, to reduce a penalty in terms of a specified number of years, or to alter it with certain conditions.
Despite the breadth of the President’s authority under the Pardon Clause, the Constitution’s text provides for at least two limits on the power:
first, clemency may only be granted for Offenses against the United States, meaning that state criminal offenses and federal or state civil claims are not covered.
Second, the President’s clemency authority cannot be used in Cases of impeachment.
In Schick v. Reed, the Court recognized that an exercise of clemency may include any condition which does not otherwise offend the Constitution
https://constitution.congress.gov/browse/essay/artII-S2-C1-3-1/ALDE_00013316/
But they didn't say that it can go unspecified.
A President cannot pardon someone for offenses in the entire US Code. They have to specify the offenses being reprieved, so they must also specify the offenses being pardoned.
At the very least, someone should go to a court to block blanket pardons until SCOTUS can rule on whether pardons can be unspecified for "any" crime in the US Code.
-PJ