PRAGUE (AP) — An heir of a Jewish art collector killed in the Holocaust is turning to US courts to sue the Czech Republic in a bid to claim a series of paintings once seized by the Nazis, a restitution expert said Thursday.

It will be the first such lawsuit by Jewish descendants from the Czech Republic in a case that could give hope to those in the country who have so far failed in their claims.

Czech restitution law allows only direct relatives, such as wives and children, to claim such stolen art. But the heir turning to US courts, Michal Klepetar, is the grand nephew of Richard Popper, the Jewish businessman and art collector.

The restitution expert advising Klepetar, Tomas Jelinek, said he decided to turn to US courts after exhausting legal options in the Czech Republic.

“He did all he could and when it turned out that it wouldn’t work he decided to go to America,” said Jelinek, who is also a former chairman of Prague’s Jewish community.

All Czech courts, including the constitutional Court, rejected Klepetar’s claims and politicians declined to address his demands.

“He approached ministers and prime ministers and nobody helped him,” Jelinek said.

In a 2011 letter to Klepetar, Prime Minister Petr Necas said he felt sorry for what happened to Klepetar’s family during the Holocaust.

“At the same time, I am of the view that it is not possible to open again the restitution process now because it would be a blow for the legal certainty and stability of property relations in an already functioning democratic system when most property belongs to private owners.”

However, an official government Website shows that at least some of the paintings currently belong to the National Gallery in Prague. Klepetar had unsuccessfully sued the gallery before.

He was scheduled to announce details of the new lawsuit together with his US lawyer on Friday.

There is some precendence for East European restitution cases in US courts. Last September, a US federal judge ruled that the heirs of a Jewish art collector could proceed with a lawsuit against Hungary in a different restitution case.

Jelinek said Klepetar is claiming 125 paintings and unspecified financial compensation with his US lawsuit.

The paintings were part of the Popper collection of mostly paintings by European old masters. During the Nazi occupation during WWII of what was then Czechoslovakia, Popper, his wife and their only daughter were transported in 1941 to a Jewish ghetto in the Polish city of Lodz, where they all died.

Klepetar’s is just one of numerous cases of looted art that have not been solved yet.

The announcement of the lawsuit came about two years after the Czech Republic and more than 40 other nations agreed in Prague on the first-ever set of global guidelines for returning property stolen by the Nazis to the rightful owners or heirs.

But many have complained not much has changed since then, and the Czech Republic and some other countries have come under fire for legal hurdles and a lack of political will in property restitution cases.