Brussels — In June a young Mexican lawyer walked out of the French Bibliotheque Nationale in Paris with a pre-Colombian Aztec manuscript under his poncho. Later apprehended in his native country, he claimed he merely wanted to restore this errant piece of national heritage to its rightful place after centuries in foreign hands.
Although this particular act of repossession gained considerable attention in the French and Mexican press, it represented only one of an increasing number of attempts by third-world countries to reclaim the vast treasure-trove of art and archeological relics scattered throughout the museums and collections of the developed nations during centuries of colonial occupation or through more recent smuggling.
The British Museum in London, the Louvre in Paris, and countless other institutions in the United States, Germany, Japan, and other affluent countries have the increasingly embarrassing distinction of housing more of the third world's cultural heritage than the originating countries themselves, according to a number of experts.
Now whenever industrial and third-world heads of state meet, the subject is just as likely to turn to the recovery of art or cultural goods as to trade and geopolitical issues.
One case frequently cited is the visit by former French Prime Minister Raymond Barre to Iraq to discuss oil deliveries and prices, only to be reminded by Iraqi President Saddam Hussein that Baghdad was just as eager to talk about the return of the 3,000-year-old Code of Hammurabi.
The crusade to return art to its homeland has also gained momentum through the efforts of the United Nations Educational, Scientific, and Cultural Organization (UNESCO) in Paris.
UNESCO's efforts have included the sponsoring of an international treaty for the return of ''cultural property.'' But the treaty has been ratified by only a handful of countries. Perhaps more effective has been its organization of committees that have become pressure groups to back up the attempts by individual countries to repatriate their purloined treasures.
Probably one of the main targets of this simmering North-South resentment has been the British Museum in London, which is literally overflowing with third-world art. One estimate is that there are some 90,000 African artifacts in the museum.
An exhibit of ''The Treasures of Ancient Nigeria'' that opened recently includes controversial Benin bronze scuptures. Taken in 1897 by a British punitive expedition that invaded Nigeria and captured Benin, they were dispersed throughout the world, in part to pay for the cost of the war.
Nigeria has asked for the return of some of them, but been turned down. Former Pakistan President Ali Bhutto also was rebuffed when he requested the legendary Kohinoor diamond that is the main jewel in the British crown. And Greek film star Melina Mercouri, now her country's culture minister, has joined in what is essentially a North-South dispute by requesting the ancient Elgin marbles from the museum.
Officials from this and other museums counter that there are few facilities or staff in the third world that could adequately care for these restored projects. They argue that in some instances goods have been returned to their home country only to be resold on the international art market.
At a recent London seminar on the subject, Salah Stetie, chairman of a UNESCO group, commented: ''Of course, we are not saying that everything should be returned to its country of origin. That would be totally unrealistic. We are just talking about returning a few objects which have a fundamental significance to a country's tradition. Just a few objects out of the thousands in Western museums.''
He cited as examples the three oldest copies of the Koran, all of which are in non-Muslim countries, and the Benin art masterpieces, none of which are left in Benin.
Although many of these discussions have been futile, some former colonial powers and other countries have returned such relics to their country of origin. Belgium, seeking to help its former colony, Zaire, develop museums, has returned some of its vast collection of Congolese art. The Netherlands has returned some art objects to Indonesia.
In a decision that was closely watched and is being appealed, a court in Torinto, Italy, recently judged that such art objects should be returned to Ecuador.
But third-world leaders, governments, and publications are pressing the issue as a major element in an ongoing dialogue with the developed countries. Most experts expect the subject to increase in importance in the future.