A little while ago i brought back from France a Verney-Carron O/U that i had inherited and had to have it inspected by the experts in the little room whilst clearing customs in Montreal. After watching the experts try to crack open the barrel with everything but a hammer i moved forward and said "let me help you open that". Big mistake. "move behind the red line sir" police called. Luckily the Officer was former military, saw my army issue luggage ... promptly cracked open the shotgun, inspected it, closed it properly, gave a dirty look to the customs guys and said "have a good day sir".
Point is, you just never know who you are going to have to deal with and a little extra paperwork in hand might just go a long way.