Andrew Johnson did it in 1866 so this one is not up for ignorance jumpin' into the fray.
Was that really comparable in a way that could be considered precedent setting for this case, though? Johnson issued nearly 13,000 pardons to higher level Confederates not included under the policy of general amnesty that included 14 ineligible groups based upon specific involvement in the war, and required recitation of the following oath:
“I, _____, do solemnly swear or affirm, in presence of Almighty God, that I will henceforth faithfully support and defend the Constitution of the United States and the Union of the States thereunder. And that I will, in like manner, abide by and faithfully support all laws and proclamations which have been made during the existing rebellion with reference to the emancipation of slaves, so help me God.”