Tariq Ramadan, a prominent Swiss-Muslim professor, hopes to visit the United States again after a federal appeals court ruled the government had not justified its visa denial.
Mr Ramadan, 47, teaches at Oxford University in the UK and has been refused a US visa several times since 2004, when he was offered a job at the University of Notre Dame in Indiana, one of the country's top Catholic universities.
The Bush administration said he gave more than US$1,000 (Dh3,673) to a Swiss-based charity later deemed by the US to support the Palestinian Hamas movement.
He is the grandson of Hasan al Banna, who founded the Muslim Brotherhood in Egypt in 1928.
A federal appeals court last Friday reversed a lower federal court and said the government's exclusion of Mr Ramadan violated the first amendment rights of US groups that wanted to meet and talk with Mr Ramadan.
Groups including the American Civil Liberties Union (ACLU) had long urged the Obama administration to lift its exclusion of the scholar.
"I am very gratified with the court's decision," Mr Ramadan said in a statement. "I am eager to engage once again with Americans in the kinds of face-to-face discussions that are central to academic exchange and crucial to bridging cultural divides."
The appeals court sent his case to the lower court, saying the government will have to "confront Ramadan with the allegations against him and afford him the subsequent opportunity to demonstrate by clear and convincing evidence that he did not know and reasonably should not have known, that the recipient of his contributions was a terrorist organisation".
The ACLU hoped the Obama administration would end his exclusion without further litigation.
"We also encourage the new administration to reconsider the exclusion of other foreign scholars, writers and artists who were barred from the country by the Bush administration on ideological grounds," said Melissa Goodman, a staff attorney with the ACLU's national security project.
Other excluded intellectuals include Iñaki Egaña, a Basque historian, Haluk Gerger, a Turkish journalist and sociologist, Dora Maria Tellez, a Nicaraguan human rights activist, and Adam Habib, a South African political commentator.
A group of academic and civil liberties organisations sent a letter to the Obama administration earlier this year saying the ideological exclusion of foreign scholars "compromises the vitality of academic and political debate in the United States at a time when that debate is exceptionally important".
The Obama administration has so far resisted lifting the ban on Mr Ramadan's entry. David Jones, an assistant US attorney, told the appeals court earlier this year that it should uphold the ban or else the government would face a "quagmire" with others seeking reversals. "Consular decisions are not subject to litigation," he said.
When Mr Jones was asked what level of the government had considered Mr Ramadan's case, he said "upwards in the state department".
Jameel Jaffer, an ACLU lawyer who argued Mr Ramadan's case before the appeals court, has urged "a clean break of the Bush administration's national security policies".
"As we've been emphasising from the outset of this case, the exclusion of foreign scholars on ideological grounds skews and impoverishes academic and political debate inside the United States," he said. "The government should not be using the immigration laws as instruments of censorship."
Mr Ramadan wrote in a court affidavit that he was unaware of links between Hamas or terrorism and the Association de Secours Palestinian, the charity he supported with donations. "I have condemned terrorism at every opportunity," he wrote.
He came eighth in a list of the world's 100 leading intellectuals in a poll conducted by Foreign Policy and Prospect magazines last year. Critics have variously accused him of anti-Semitism, covertly trying to convert the West to Islam or identifying too closely with western values.
In his latest book, Radical Reform: Islamic Ethics and Liberation, Mr Ramadan again urges his fellow Muslims to participate fully in the civil life of the western societies in which they live. He argues against those who believe reform is a dangerous and foreign deviation or a betrayal of the faith, saying authentic reform has always been grounded in Islam's traditions.