Panda exchanges, like the one that sent two bears to Washington’s National Zoo this week, are governed by closely held contracts. In most countries, they are never released.

Lawyers for the Smithsonian, which operates the National Zoo, cited a confidentiality clause and refused to release a 2020 contract. The U.S. Fish and Wildlife Service, which regulates the import and export of exotic species, provided a San Diego Zoo contract with key passages blacked out.

But my colleagues and I found full copies of those documents and others in regulatory filings.

The contracts govern two pandas at the National Zoo and two more that arrived in San Diego this summer.

Comparing these contracts with past agreements revealed that American zoo administrators are ceding increasing authority to the China Wildlife Conservation Association, a government group that administers many panda agreements.

China’s national forestry bureau, which oversees the wildlife group, did not respond to a request to comment.