All I want to do here is give you the full text of the order from the King's own hand so you can read it for yourself. On December 10th, 1770, here was the order given by King George III:
947. No Additional Duties on Slaves in VirginiaWhereas at a general assembly begun and held in our city of Williamsburg in our colony and dominion of Virginia on the seventh day of November in the tenth year of our reign, two laws were framed and enacted by our governor, council, and House of Burgesses of our said colony and dominion of Virginia, entitled An Act for Laying an Additional Duty upon Slaves Imported into This Colony, and the other An Act for the Better Support of the Contingent Charges of Government, by which said laws additional duties, amounting to fifteen per cent were imposed upon every purchase of slaves imported or brought into that colony over and above a duty of ten per cent payable by former laws then in force; and whereas it hath been represented to us that so considerable an increase upon the duties of slaves imported into our colony of Virginia will have the effect to prejudice and obstruct as well the commerce of this kingdom as the cultivation and improvement of the said colony; whereupon we have thought fit to disallow the first mentioned of the laws, leaving the other, which is of short duration, to expire by its own limitation. It is therefore our will and pleasure that you do not upon pain of our highest displeasure give your assent for the future, without our royal permission first obtained, to any law or laws by which the additional duty of five per cent upon slaves imported, imposed by the last mentioned law, shall be further continued or to any laws whatever by which the duties of ten per cent upon slaves imported into our said colony, payable by laws passed antecedent to the seventh day of November, 1769, shall upon any pretense be increased or by which the importation of slaves shall be in any respect prohibited or obstructed.
Virginia: (§939); Dec. 10, 1770.
Source: Royal Instructions To British Colonial Governors 1670 - 1776 Volume II, page 679.(counted as page 232)