Jailed in Madrid on an extradition request from the United States that his lawyer says is tied to pro-Palestinian activism, James Chambers fears persecution if returned. James Chambers is a former heir to a media fortune who broke with his family in a deal he said was worth hundreds of millions. After the Oct. 7, 2023, Hamas-led attack on Israel, Mr. Chambers championed the Palestinian cause, attended protests, and paid bail and legal fees for people arrested at actions targeting Elbit Systems, an Israeli defense contractor.

Mr. Chambers, 41, was arrested in Ibiza in July, and a council of Spanish government ministers is expected to consider the issue on Tuesday. His lawyer, Baltasar Garzón, dismissed the U.S. case as strictly political, saying it was part of a wider U.S. campaign against people who have a concrete stand on Palestine. The U.S. money laundering accusation is tied to a transfer of more than $7 million to Tunisia after Mr. Chambers left the United States, funds that paid debts and salaries for a Tunisian soccer team.

His client's money comes from the deal he made with his family to cut ties in 2023 with Cox Enterprises, and was spent on legal causes. The defense contends that the United States aims to taint Mr. Chambers's legitimate donations based on his stated opinions, criminalizing aid to Palestinians. Pressure is growing in Spain to limit cooperation with the United States over the case.