NEW YORK, NY.- Twenty-five years after 44 countries endorsed the landmark Washington Principles on returning Nazi-looted art, a smaller group of nations led by the United States has signed an agreement designed to reinforce those guidelines by clarifying ambiguities that have allowed for differing interpretations and spurred disputes.

The new agreement, called “Best Practices for the Washington Principles on Nazi-Confiscated Art,” was presented Tuesday at a ceremony in Washington at the United States Holocaust Memorial Museum.

Since the Washington Principles were adopted in 1998, they have been credited with creating a moral framework that has greatly accelerated the return of art stolen, or sold under duress, during the Nazi era. Though the agreement is nonbinding, nations pledged to abide by 11 guidelines that seek to promote “just and fair” solutions in the settlement of restitution claims.

But there have been disagreements over how the principles should be interpreted and applied, and that led to some confusion and conflict.

For example, some interpreted that “just and fair” solutions would take into account the well-being of the current holder of stolen art, not just the family from whom it was taken. So, in the Netherlands, the panel that adjudicates restitution claims had used a “balance of interests” policy, in which the interests of claimants were weighed against those of Dutch museums that now held the works.

After fierce criticism, the Dutch government commissioned a review that led to the policy being scrapped in 2020.

The new guidelines announced Friday make it clear: “‘Just and fair’ means just and fair solutions first and foremost for the victims of the Holocaust (Shoah) and other victims of Nazi persecution and for their heirs.”

So far, 22 countries have signed on to the new agreement, and the leaders of the initiative — the U.S. State Department and the World Jewish Restitution Organization — say they expect more to join.

“These best practices more precisely define what is considered Nazi-looted art,” Secretary of State Antony Blinken said in prerecorded remarks screened at the ceremony. “They identify solutions when provenance research is lacking. They remedy processes that favor current possessors over rightful owners. They urge countries to bolster their restitution efforts.”

Though only nations signed on to the Washington Principles 25 years ago, they have since been more broadly embraced by museums and the art world as a whole as an important moral guidepost.

Stuart Eizenstat, the secretary of state’s Special Adviser on Holocaust Issues and a key architect of the original principles, said in an interview, “It’s a great example of how voluntary international principles, if they’re undergirded by strong moral and ethical principles, can have a dramatic impact.”

However, “there’s still a huge amount of work to be done,” he said. The new guidelines “are taking 25 years of experience and seeing where the gaps are, where we could strengthen the principles and create a new momentum.”

The original Washington Principles and subsequent agreements reached in Vilnius, Lithuania, and Terezin in the Czech Republic spurred a number of countries to adjust their laws in favor of Nazi-looted art claimants and to promote research into the ownership history of art in public collections.

Germany, Austria, Britain, the Netherlands and France established commissions to adjudicate claims for works in public collections, in line with the accord’s recommendation for bodies “to identify art that was confiscated by the Nazis and to assist in addressing ownership issues.”

Eizenstat said the Washington Principles created a “ripple effect,” paving the way for Western museums to return looted objects to former colonies, such as the restitution of hundreds of Benin Bronzes to Nigeria. Provenance research into the history of artworks has also expanded worldwide.

“All of this is connected and just wouldn’t have happened otherwise,” he said.

Among the clarifications put forward as part of the best practices is guidance on what constitutes a so-called sale under duress. Jews in Nazi Germany and occupied lands were sometimes forced to sell their art, often at a discount, to cover living expenses after they were barred from their professions or to pay punitive exit taxes before they fled.

The Washington Principles did not specifically address how to handle such claims.

In 2009, the Terezin Declaration, a broader agreement signed by 47 countries that also covered Holocaust education and survivors’ welfare, clarified that the need to find “just and fair” solutions to looted art extended to works that had been sold under duress. But museums have frequently argued that claimants must prove a sale was made under duress, particularly if it took place before 1936. That kind of evidence can be difficult to find because Jewish collectors who fled generally took few documents with them.

The new “best practices” presented Tuesday lift the burden of proof from the claimant, stating that any art sale “by a persecuted person during the Holocaust era between 1933-1945 can be considered equivalent to an involuntary transfer of property based on the circumstances of the sale.”

Olaf Ossmann, a Swiss lawyer who works on art restitution cases and helped to draft the new guidelines, said: “Now it’s up to the current holder to prove the exemption from this general rule.”

The “best practices” also refine the Washington Principles’ call on governments “to create an independent expert body” to “adjudicate cases of art and cultural property.” The new guidelines specify that “unilateral access” to such panels should be available, meaning heirs should be able to submit claims for evaluation without needing the consent of the current holder.

This is currently a hot-button issue in Germany, where the government’s advisory commission is authorized to adjudicate claims only if both parties agree.

Claudia Roth, the German culture minister, has promised to extend the panel’s remit and allow it to evaluate a claim even if the current holder of a contested work resists. At an event last year to mark the 25th anniversary of the Washington Principles, Roth said the advisory commission’s current mandate is “inadequate,” adding that Germany is “not living up to our responsibilities.”

But her attempts to reform the German advisory commission have until now been blocked by the 16 state governments. The Bavarian government, in particular, has voiced its opposition to the change — and has so far rebuffed calls to submit a dispute over Pablo Picasso’s 1903 “Portrait of Madame Soler” to the advisory panel.

“Germany, which has done so very much in other areas, has really lagged in art restitution,” Eizenstat said. “The Germans have the most responsibility and they should be the leaders.”

Even so, Germany is one of seven countries named as having made “major progress” in implementing the Washington Principles in a report by the World Jewish Restitution Organization and the Claims Conference published Tuesday. The other six are Austria, France, the Netherlands, Britain, the Czech Republic and the United States.

Canada, Israel and Switzerland were judged to have made “substantial progress.” An additional 13, including Croatia, Italy, Sweden and Poland, have made “some progress,” the report found. Twenty-four countries that endorsed the Washington Principles have made “little or no progress,” including Russia, Finland, Australia and Ukraine.

“This report shows both the progress made and the immense work still to be done to secure justice,” said Gideon Taylor, the president of the restitution organization.

This article originally appeared in The New York Times.