The government is increasingly using secret evidence allowed under new antiterrorism laws to prevent certain critics from entering the United States, according to a group of civil rights and academic organizations.

The group, led by the American Civil Liberties Union, went to court yesterday in Boston seeking to force the State Department and the Department of Homeland Security to grant an entry visa to a South African Muslim academic who they said was barred from the United States because of his criticism of American foreign policy.

“It sends the message that we are afraid of engaging difficult ideas,” an A.C.L.U. lawyer, Melissa Goodman, said.

Ms. Goodman said that it was possible that some people barred were a threat but that the fact that the reasons for their exclusion were kept secret made such cases difficult to evaluate.

Leftists traditionally bear the brunt of such exclusions, the various organizations suing said, but there has been a significant increase in such cases involving Muslims since the terrorist attacks of Sept. 11, 2001.

Under the McCarran-Walter Act of 1952, which was written in part to limit the entry of communists or their sympathizers, the United States has had a history of barring prominent intellectuals. Those denied entry visas over the years under McCarran-Walter have included the writers Gabriel García Márquez and Graham Greene as well as political figures like Pierre Trudeau, long before he became prime minister of Canada.

“It sometimes does seem that what the government has done is taken the communist-era playbook and replaced every instance of the word communist with terrorist,” said Jameel Jaffer, an A.C.L.U. lawyer who said those excluded rarely appeared to be national security threats.

Critics also say the exclusions are making Americans increasingly isolated from international opinion. They say that at a time when the United States is seen by many foreigners as arrogant, it is important to admit foreigners and to let them express their opinions, if not necessarily endorse them.

“We see it as violation as our First Amendment rights as Americans to engage in international ideas and with international figures face to face,” said Larry Siems, director of Freedom to Write at the PEN American Center, an international organization of writers. “To impose new barriers at the border is an act of international antagonism.”

Supporters of exclusion say the A.C.L.U. and other organizations are ignoring the welter of opinions that reach Americans, and some argue that exclusions made under the USA Patriot Act are weaker than the 1950s legislation.

“What the A.C.L.U. and those extreme liberal groups are trying to do is focus a magnifying glass on a small part of the picture rather than focus on the entire picture,” said James R. Edwards Jr., an immigration expert and adjunct fellow at the Hudson Institute, a Washington public policy group.

“There are certainly some diverse opinions from foreigners that are voiced regularly in this country,” Mr. Edwards added, pointing, for instance, to the speech on Monday by President Mahmoud Ahmadinejad of Iran at Columbia University.

The lawsuit filed yesterday, in Federal District Court, names as defendants — in addition to the State Department and the Department of Homeland Security — Condoleezza Rice, the secretary of state, and Michael Chertoff, the secretary of homeland security. It seeks to force the government to issue a visa for the South African Muslim academic, Adam Habib, who has been a vocal critic of United States foreign policy in the Middle East.

Other organizations who joined the lawsuit, and who had sought Mr. Habib as a speaker, included the American Sociological Association, the American Association of University Professors, the American-Arab Anti-Discrimination Committee and the Boston Coalition for Palestinian Rights.

Mr. Habib, who obtained his doctorate from the City University of New York, was a frequent visitor to the United States until his visa was revoked last October.

Neither the Department of Homeland Security nor the State Department would comment on the lawsuit.