There is no specific exemption in the USBC for decks, therefore I would strongly suggest that you ask the building official of the jurisdiction for an interpretation. However, I believe you can apply the accessory structure permit exemption provided that the exception under 403 for footings is met which would also mean the guardrail height trigger has not been exceeded AND the structure does not carry a structural load like a hot tub. Prince William exempts no load bearing decks that are 16.5 inches or below to grade from requiring permits. The technical provisions of the code still apply, they just don’t need to be verified/confirmed by a permit and inspections.
Sean P. Farrell