BOSTON — A court filing here yesterday by the American Civil Liberties Union could open the way for a South African scholar accused of having links to terrorism to meet with scholars at Columbia University, the World Bank, and the Graduate Center at the City University of New York.

The case of Adam Habib, deputy vice chancellor at the University of Johannesburg, is being taken up by the ACLU, the American Sociological Association, the American Association of University Professors, and the American-Arab Anti-Discrimination Committee, among other groups. Mr. Habib has written about his case on the Huffington Post Web site.

Customs and border officials denied Mr. Habib entry to America at John F. Kennedy International Airport in October 2006 when he arrived to meet with affiliates of Columbia, the World Bank, and the Gates Foundation. Last month, the State Department denied Mr. Habib a visa.

America’s senior consul in Johannesburg, Charles Luoma-Overstreet, told Mr. Habib in a letter, supplied to The New York Sun by the ACLU, that the State Department “upheld a finding of your inadmissibility under section 212(a)(3)(B)(i)(I),” described as pertaining to those having “engaged in a terrorist activity.” Yesterday’s legal filing challenges that decision.

A spokeswoman for the State Department, Leslie Phillips, declined to comment on Mr. Habib’s case, saying the department does not discuss individual visa cases. The Department of Homeland Security did not respond to a call seeking comment.

Mr. Habib is a critic of the American government, but he and his advocates deny any terrorist links. “Am I critic of the U.S. Government? Absolutely,” he wrote in September on the Huffington Post. In a 2003 New York Times story, he called American foreign policy a “combination of gunboat diplomacy and checkbook diplomacy that undermines other kinds of diplomacy.”

“We think this is a clear violation of academic freedom,” a professor of political science and sociology at CUNY who taught Mr. Habib at the university and invited him to speak at the American Sociological Association’s annual conference, Frances Fox Piven, said. “He would be much in demand as a speaker at the sociology program at the Graduate Center at the City University of New York, New York University, and a number of other institutions.”

An ACLU attorney handling Mr. Habib’s case, Melissa Goodman, said the government is pointing “to a statute that covers people who have engaged in terrorist activities. We know of no basis for that accusation.” The ACLU’s contention, she said, is that the professor’s exclusion is part of a government pattern of barring “vocal critics of U.S. policy.”

An adjunct fellow at the Hudson Institute, James Edwards, disputed that notion. “The fact is that the government has access to more sensitive information that they … can’t disclose for national security reasons,” he said. “At some point, you have to trust the fact that the guys who are losing sleep every night trying to keep us safe know what they’re doing.”