Portaure wants you to help him smuggle some goods into Jeuno. If you accept the quest, you'll obtain the temporary key item:Brugaire Goods.
Take the Airship to Jeuno and pass through customs.
To earn an extra 500 gil, consider accepting the San d'Orian version of the quest "A Discerning Eye" as well.
Passing through and clearing Jeuno customs is required to complete this quest. It is possible to complete this quest after traveling to Jeuno by other means, bypassing the airship ride. To pass through customs once in Port Jeuno, pay your way past the Departures Exit door at the Port Jeuno-San d'Oria travel agency. Then you can immediately examine the Arrivals Entrance. This will pass you through Jeuno customs. There is no way to bypass the 200 gil airship fee.
If you pass through customs untroubled, continue with the walk-through.
There is a random chance customs will stop you. They will seize the Brugaire Goods and revoke your Airship pass until midnight Japan time. This only restricts you from boarding flights leaving Jeuno, not those departing from other areas.
You must return to Portaure to try again, however as long as your flight privileges are revoked, he will not re-flag this quest.
Until you speak with Yin Pocanakhu or until the Brugaire Goods are confiscated, you will be checked by Port Jeuno customs each time you pass through arrivals from San d'Oria. This quest can fail as long as you have the Brugaire Goods, even if you cleared customs once before.
It is possible that Yin Pocanakhu will not accept the Brugaire Goods due to their "extensive damage." This possibly results from engaging in combat while carrying the key item. Also if you teleport, you HAVE to take the airship.