The jumpseat priority list is/maybe an FOM document but it is not a regulatory agreement with the FAA. The FARs state the captain is PIC and controls access to the jumpseat. Each company I've worked for has stated that the captain makes the final determination as to who will occupy the jumpseat. No priority list overrides the PIC so the idea that big brother FAA is going to come down on a pilot for taking a United pilot over a UPS or a Republic pilot is ridiculous dramatic over reaction.