Guernsey’s auction house in New York has called off an auction of Nelson Mandela’s possessions.

The South African government objected to the sale, which was scheduled to take place later this month, arguing that several items on the block, including the key to Mandela’s prison cell, had been illegally exported from the country.

“We had a major controversy come up,” Guernsey’s president, Arlan Ettinger, told Page Six. The South African Heritage Resources Agency, he explained, had “determined that these items were potential national treasures, and hence when something is designated [as such], it requires permits to leave South Africa.”

Mandela, who died in 2013, spent 27 years in jail on a sabotage conviction before his release and election as the nation’s president. The maximum security facility at Robben Island, where he was imprisoned for 18 years, has been closed since 1991, and now operates as the Robben Island Museum, a South African National Heritage Site and a UNESCO World Heritage Site.

Many of the items in the cancelled auction were consigned by family members of the anti-apartheid revolutionary. The sale was intended as a fundraiser for a memorial garden and museum dedicated to Mandela’s life and activism at his burial site.

The 33-lot sale, “Important Artifacts from the Life of Nelson Mandela”, was scheduled for January 28, and was expected to bring in $5 million.

Other objects included examples of Mandela’s artworks, including a painting of the lighthouse on Robben Island and a black and white drawing of a chain being broken, as well as a signed handprint and a bronze cast of his fist.

Some of Mandela’s personal effects that would have been on offer were a patterned silk Madiba shirt and a pair of Ray-Ban aviator sunglasses. There were also presents from other world leaders, with a blanket gifted by U.S. President Barack Obama, and a set of pens from George W. Bush.

The key to Nelson Mandela’s jail cell on Robben Island. Photo courtesy of Guernsey’s.

The most controversial item, from South Africa’s perspective, was the prison cell key, consigned by Christo Brand, a Robben Island guard, along with a tennis racket and exercise bike that Mandela used during his incarceration. There was also a copy of the South African constitution with an inscription by Mandela to Brand, who became close friends.

“It is unfathomable for Guernsey’s, which is clearly aware of the painful history of our country and the symbolism of the key, to consider auctioning the key without any consultation with the South African government,” Nathi Mthethwa, the nation’s minister of sport, arts, and culture, said in a statement last month to the Associated Press. “The key is living proof of South Africans’ long walk to freedom and belongs to the people of South Africa. It therefore must rightfully be returned to the country.”

Now the auction house is caught in the middle of a stand off between the Mandela family and the South African government, both of which believe the items should be returned to them.

See more lots from the sale below.

Barack and Michelle Obama gave this blanket to Nelson Mandela as a gift. Photo courtesy of Guernsey’s.

A drawing Nelson Mandela of a chain being broken. Photo courtesy of Guernsey’s.

One of Nelson Mandela’s signature patterned silk shirts, called Madiba shirts after his Xhosa clan name. Photo courtesy of Guernsey’s.