I assume of course that laws will differ by country, and I'm interested in those differences, though there should be some common aspects.
There are several layers to my question.
We agree that your friend can bring you a gift from his homeland, as long as it complies with custom rules.
Now can your friend legally sell it back to you at the price he bought it ?
This product may sometimes be available in your country, but at higher price, does it change anything ?
Can your friend legally sell it back to you at a higher price, making some pocket money out of it ?
Now what if he's not a friend, but a stranger, or someone you got acquainted with online, is it considered contraband? (assuming everything is ok with customs at the airport).
Does it change anything if it's done between European Union countries?
Does it change anything if it's recurrent ? e.g. say this guys comes every month from Russia to France for unrelated business, each time he fills up his luggage with the maximum allowed amount of goods that comply with custom laws, and I buy them, giving him 15% of margin, is that OK?