I was asked about U.S. customs. There was just so many different facets about U.S. customs that I am gonna put a link to a website that should answer most questions. The main point is that customs monitors and tracks anything coming in and going out of the country. Customs does NOT need a warrant to open a pack or search a vessel/plane/or cargo. As stated they monitor and track everything from planes/boats/cargo/mail/and on person. Each person has to declare what they are bringing in and the approx. cost. Now in our game, we usually have shipped in international goods. Each pack has a tracking number that is associated with it from the very beginning of the first mailing. It can be tracked via internet, but usually customs is a bit behind in their updates. If you can get a product without a script in a certain country but requires a script here, it is illegal without that script in the U.S. that is why a lot of us get a customs letter when a product is searched and seized. Here is the link.
HowStuffWorks "How the U.S. Customs Service Works" 
U.S. Customs 
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