Except he had been sworn into regular army service after Initially being organised under partisan ranger act. Not aware that was ever rescinded.
Its why his company had fought with regular cavalry at PG, they had been sworn into regular service prior. Again, in special orders 45 Maj Gen Hindmann ordered Maj J P Wilson to proceed at once to muster into the Confederate Service for 3 years, or the duration of the war, Captain Quantill Missouri cavalry company of 76 men rank and file on Nov 18th 1862
Then special Orders 46 by Hindman again has Capt Quantrill and his Missouri company report to Gen Marmaduke for duty, leading to them participating in PG.
That the partisan ranger act was disbanded, didn't affect companies sworn into Confederate cavalry service, it affected companies only operating under the act. The disbandment of the act would have affected very few troops at the time, as it was a provision for men to organise behind lines, once reaching the lines, most like Quantrill were swore into Confederate service which would then supercede the PRA organisation.