GENEVA (AFP).- How to define Nazi-era "loot" is central to what could prove a touchy book launched Tuesday on the controversy surrounding one of Europe's most prestigious private art collections, the impressionist works acquired by E.G. Buehrle.
The late industrialist amassed a fortune selling weapons to both the Nazis and the Allies during World War II, wealth that helped buy several hundred artworks -- some from Jews under threat -- that will soon go on show at one of Switzerland's leading museums, the Kunsthaus in Zurich.
The book, "Schwarzbuch Buhrle" ("Buehrle Black Book") offers a new challenge -- is it morally defensible to display such paintings, especially in a museum that receives public subsidies?
"The city of Zurich and the Kunsthaus have to be very careful how they are handling this collection because the damage for the reputation of the city could be serious," co-author Thomas Buomberger told AFP.
The Buehrle Foundation itself confirms that 13 paintings bought by the German-born industrialist, who later acquired Swiss citizenship, had been stolen by the Nazis from Jewish owners in France.
Following a series of court cases after the war, Buehrle returned all 13 pieces to their rightful owners then repurchased nine of them, the foundation said.
While these transactions were aimed at giving legitimacy to the entire Zurich-based collection, Buomberger's research focuses on pieces sold by Jews under duress, possibly while fleeing for their lives.
For him, the term looted art should apply to "all transactions which would not have taken place if the Nazis had not been in power, which means of course works of art that were sold in Switzerland by Jews who had to flee."
If any painting sold by an owner who faced imminent threat from the Nazis can be categorised as war loot -- as the German term for such pieces, Fluchtgut, or escape-goods, would indicate -- then much of the Buehrle collection, and pieces across Switzerland, fall under suspicion, Buomberger told AFP.
"I am speaking of hundreds if not thousands of works of art," he said.
- Willing seller? -
Kunsthaus spokesman Bjoern Quellenberg disagrees. Works sold under duress, he said, "cannot be regarded from the same perspective as the looted art, not at all."
He said the museum had long dealt with the Buehrle Foundation and has tried to swiftly address any questions about the works' provenance. He also confirmed that the Kunsthaus plans to display the entire Buehrle collection when its new wing is completed in 2020.
Talks on transferring the paintings to the museum began in 2002 but accelerated after a spectacular 2008 heist in which men disguised in ski masks stole four 19th-century masterpieces at the Buehrle Foundation, a theft that shocked the country.
But Buomberger pointed to one piece that he said highlighted outstanding questions -- "La Sultane" by Eduoard Manet, which his research showed had been owned by a man named Max Silberberg who died at Auschwitz.
He insisted there was a moral obligation to seriously investigate the circumstances that led Silberberg to sell. "It is not something to be done if you have time and money. It is really a duty to fullfil."
For the museum spokesman, Buomberger has set impossible criteria.
"The Fluchtgut does not fall under convention. It's not a term which can be legally employed or legally binding to anybody," Quellenberg told AFP.
Even the Washington Principles, guidelines signed in 1998 by Germany and more than 40 other countries on dealing with art stolen in World War II, speaks specifically about works "confiscated by the Nazis" not art sold by Jews and other persecuted people who had to escape, he said.
"The accusations from Mr. Buomberger, they don't have a point, really," said Quellenberg.
- With wealth comes 'shadows' -
Buomberger's book also delves into the Buehrle family history, not only E.G.'s lucrative dealings with both sides during the war but also the maligned politics of his son, Dieter.
After the father died suddenly in 1956, Dieter formed a particularly close relationship with apartheid South Africa as he looked to expand business outside Europe.
P.W. Botha, the former South African president and unrelenting defender of white minority rule, gave Dieter an honour for "meritorious service".
"This background is also important," said Buomberger.
Quellenberg said such biographical details were not the Kunsthaus's concern.
"We mainly focus on the works. We do not deal with the family history at all... No matter where you look in the world, if you have a big family name, even the Rockefellers, you never say their money was always clean," he told AFP.
"So, in the art world, as well as everywhere there is wealth, there are some shadows."
© 1994-2015 Agence France-Presse