Feelings still run high in Russia and Japan over a territorial dispute which has hampered relations for almost 60 years, writes Daniel McLaughlin, in Moscow.
It was the colour of the islands that offended the customs inspector.
They were the same shade on the map as Japan, not Russia, and that was no minor detail in this part of the world, and when the countries concerned were still technically at war.
The map showed four small islands in the northern Pacific Ocean, barren chunks of land that Moscow calls the Southern Kuriles, but which Tokyo insists are still its Northern Territories. Soviet forces seized them at the end of the Second World War, and ever since Japan has refused to sign a peace treaty formally ending hostilities.
The offending map was part of a calendar called, in Japanese, "Flora and Fauna of the Northern Territories". When the customs officers at Sakhalin in Russia's far east realised this, they knew what to do.
"Since Soviet times," intoned customs spokesman Mr Yuri Gurshal on Russian television yesterday, "the importing of video, photographic or printed material violating the integrity of our borders has been prohibited. Therefore the decision was taken to return the confiscated calendars to Sapporo".
It was a sharp reminder to President Vladimir Putin and Prime Minister Junichiro Koizumi, just days after they held cordial meetings in Moscow, that feelings still run high in Russia over the islands that have hampered Russo-Japanese relations for almost six decades.
Feeling is at least as strong in Japan. On Mr Koizumi's return to Tokyo, the Japan Times lamented that the territorial dispute seemed to be lower on his agenda than on that of any previous leader, each of whom had made resolving the Northern Territories problem a precondition for more harmonious relations with Moscow.
But Mr Koizumi and Mr Putin had other things to consider in Moscow, aside from the mutterings of their nationalist constituency.
The main outcome of their summit, which was dominated by North Korea's withdrawal from the Treaty on the Non-proliferation of Nuclear Weapons, was an "action plan" for co-operation in, above all, the energy sector.
The main feature of this is a proposed $5 billion oil pipeline from Angarsk, near Lake Baikal in Siberia, to the Pacific port of Nakhodka, some 4000 km to the east. From here, Russia could ship its top export earner, oil, direct to the west coast of the US and, most importantly, to Japan.
The project could oust plans for a cheaper pipeline through China, while easing Japan's reliance for energy on the Middle East and giving Tokyo some influence in Russia's underdeveloped far east, where Mr Koizumi fears losing out to Beijing and Washington. On his way home he stopped off in the far eastern city of Khabarovsk for talks with influential local Russian leaders, whose regions would be shut out if the Chinese route was selected.
None of which is of much concern to the 16,000 or so people who inhabit the Southern Kuriles. Infrastructure on the islands is rumbling and the only major industry - fishing - is controlled by ruthless Mafia groups.
According to Japanese and Russian reports, fishing boats from both countries often sail loaded with electrical goods, and even prostitutes, which are distributed to customs officials in return for their complicity.
The Japanese Fisheries Association estimates annual illegal trade in seafood between the two countries at $1.2 billion. Environmental groups have warned that such unregulated plundering of the sea could destroy the vital fish stocks around the Southern Kuriles.
The islanders have never been asked who they would like to govern them, and Mr Putin is unlikely to address such a sensitive issue ahead of presidential elections in 2004. Nothing looks likely to change in the near future, and the South Kuriles will go back to being a dull but nagging ache for Tokyo and Moscow, capitals of nations that are still officially at war.
The newsreader reporting the deportation of the calendars commended the customs officials' "excellent knowledge of geography".
The correspondent on the scene assured him: "This attempt to commit cartographic expansion has been thwarted."