If you mean there are sometimes reasons for import tariffs, then that might be true (it's a large debate in economics). I don't see why copyrighted goods should be treated specially, though. If a country wants an import tariff on books, just like on sugar or on steel, in order to maintain price differences, it should institute it directly, rather than via this roundabout copyright route.
Tariffs actually achieve just the opposite - it increases the cost of foreign imports. Also, it does it for everybody, also for authorized importers/resellers.
Well, sometimes there is hardly anything else but copyright that constitutes products (e.g. media, books). Personally, I would also enable the same kind of protection for trademarks (so that iPad could be sold for different price in West and elsewhere).
