I would say when you go on holiday, and traveling to a foreign country, you should should know the customs law of that country
For instance when leaving Italy, not every tourist is aware of this law, and if caught you can find your selfs in big trouble with Italian police
Buying fake goodies, like a Gucci Gag at a fraction of the price, could land you with a €10,000 fine. I have seen one tourist a few years back, flying out from Malpensa Airport in Milan, and she had a fake bag, and was soon in cuffs