Except selling them to a WA resident in ID... they would be guilty of importation into WA when they return home... right(?) No different than if a WA resident purchased online and tried to have them shipped in... although... much less trace/enforce-able.It stands to reason that it would also be legal to take already owned mags to ID and sell them to an ID resident OR a resident of WA (or any state) as long as the transaction takes place in ID.