Washington — Adam Habib, a prominent South African scholar who was deported on arrival at a New York airport in October 2006 and whose visa was subsequently revoked, did manage to gain an audience in the United States this afternoon — via a telephone link.

Mr. Habib, a deputy vice chancellor of the University of Johannesburg, spoke to scholars gathered here for the annual meeting of the American Association of University Professors. He has not been granted a new visa to enter the United States since the 2006 episode.

On June 25 a lawsuit filed by the American Civil Liberties Union on behalf of numerous scholarly associations, including the AAUP, that have invited Mr. Habib to attend meetings in the United States will be heard in a federal court in Boston.

The lawsuit asks that the federal government justify its grounds for barring Mr. Habib from entering the country. A letter sent to him by the U.S. State Department cites the scholar’s unspecified involvement in “terrorist activities” as the basis for its actions.

Mr. Habib, who is one of several foreign academics banned from the United States, has been a fierce critic of the policies of the Bush administration, and he told the audience today that he believes his ban from travel to the United States stems from his address at an antiwar rally in this country in 2003. He added, however, that in the absence of a detailed explanation from the U.S. government, his theory was “complete speculation.”

A photograph of the professor was projected onto a large screen at the front of the room as he spoke. “If you find that annoying,” said Martin Snyder, director of external relations for the association, during his introductory remarks, “you might want to write to your congressman or senator about that.”

Mr. Habib’s address focused on parallels between challenges to academic freedom in the United States and in his home country, but he did preface his remarks by observing that the association’s invitation to speak — even by telephone — was a demonstration of “the most noble traditions of the American academy.”

In contrast with his own case, Mr. Habib noted that most of the threats to academic freedom in the United States and in South Africa were not overt cases of government repression, but rather pressures to conform to “the national consensus of elites” and institutional self-censorship.

He also called on academics to “hold hands across national boundaries” not only to support academic freedom, but also to bolster what he called “a common humanity.” —Richard Byrne