I'm not planning on doing this myself (I'm not in a geographical position to either), but I just thought about the idea, and I wonder what type of rules are in place to prevent it.
This question could easily be too broad (differ from country to country), so I'll just say the two countries involved are Norway and Sweden.
Bob, Elise and Camilla are Norwegians traveling to Sweden.
Product A is much cheaper in Sweden than in Norway. Toll regulations say each person can bring only one unit of product A back to Norway from Sweden without paying toll.
While in Sweden, Bob, Elise and Camilla buy 20 units of product A. When they are very near the Norwegian border, they stop somewhere.
- Camilla gets out of the car, and keeps 18 units with her.
- Bob and Elise bring two units across to Norway.
- They stop very near the border, on the other side. Bob gives his unit to Elise and goes back to meet Camilla again in Sweden.
- They repeat the process, driving back and forth like this, bringing one unit at a time, until all the units are in Norway. They then drive happily into the Norwegian sunset with their stock of product As.
What rules are in place to prevent this type of behavior?
I limited it to Norway (to prevent it from being too broad). But is there a generally prevalent way (rules, etc.) that governments around the world use in an attempt to make this behavior impossible or difficult?
One thing I can think of is that you could have a rule that each person can only bring one unit within a timespan of 24 hours. But how is that enforceable? How would they keep track of which individual has already brought what? And often, if you are within the duty free limit, you don't have to declare it. If they check you, you are only carrying one unit, which is legal. I guess they could have a rule that says even the duty free quota must be declared and linked to your passport in a computer system. Then they could have hefty fines for not declaring even the duty free quota coupled with random sweep checks. But what do they actually do?