i wont buy it on ebay because u cant know if the guy who sold it to you didnt open it and read the code if there is one and i belive there is one i know some one in us but i am afraid that the airport will take it the costoms or what ever its called
There are protections from eBay and Paypal that prevent those kind of things.
First of all, you have the seller ratings, if 99% of people are happy with the sellers products, they aren't opening the box and trying to cheat the customer. And then there are the ratings, if the seller labels something "new in box" and it has been opened, you can return it at the seller's expense. If the seller doesn't do it, you can contact eBay or Paypal and get a refund.
And then there are eBay store fronts, that run a whole business out of eBay, rather than paying for a store front. If you buy from someone who is a legitimate business, they cant do something like what you said, or they would get fraud lawsuits.