In the latest twist of a prominent German-Swiss family's controversial art collection, its long-standing curator is stepping down.

Lukas Gloor will step down at year-end as director of the Buehrle foundation, which curates the art collection of the eponymous family, he told «Sonntagsblick» (in German) in an interview on Sunday. He will remain at the family's disposal in an as-yet undefined role, he told the Swiss weekly.

The curator's exit is the latest chapter in a decades-long saga over Emil George Buehrle, a weapons manufacturer who began collecting European sculptures and paintings in the post-war years. It includes works by French impressionists Monet, Cézanne, Gauguin, van Gogh, and Degas.

Controversial Provenance

Gloor has overseen the collection for nearly two decades and shepherded many of its works into an 206 million Swiss franc ($224 million) David Chipperfield-designed addition to Zurich's art museum. The expansion, situated between the Grossmuenster church and the city's university, has sparked controversy due to the provenance of some of the pieces of Buehrle's collection. 

Swiss historian Erich Keller has highlighted the issue in a German-language book «Das kontaminierte Museum,» which translates as «The Tainted Museum». Keller's reporting received little notice in domestic press – at least until it was picked up in a «New York Times» piece last month on the Buehrle art's Nazi legacy. A Swiss outlet subsequently dubbed him a «firebrand».

Veiled Threat To City

 The Buehrle legacy has been troubled for years: Gloor, the curator, told «Sonntagsblick» he opposes another review of the collection's provenance. The controversy is emblematic of how insular Swiss views on Nazi-associated art differ from international ones. 

He also issued a veiled threat to yank the works from public view if city officials back an outside review. «If the city of Zurich dictates to the art museum how the Emil Buehrle collection is explained to the public, we can no longer participate,» he told the outlet, without elaborating.

Buehrle's descendants control Ihag, a wealth manager Emil Buehrle founded in 1949 and which recently drew controversy in a U.S. tax matter.