Ms. Ghuman is certainly not alone in her frustration. Academic and civil liberties groups point to other foreign scholars who have been denied entry without explanation at an airport, or refused a visa when they applied. A pending lawsuit by the American Civil Liberties Union contends that the Bush administration is using heightened security measures to keep foreign scholars out on ideological grounds in violation of the First Amendment rights of American scholars to hear them.

But Ms. Ghuman’s case does not seem to fit such a pattern. Few believe that her book in progress, “India in the English Musical Imagination, 1890-1940,” or her work on Elgar, best known by Americans for “Pomp and Circumstance,” could have raised red flags in Washington. And if it were a question of security profiling, nothing in her background fits.

She was born in Wales. Her mother is a British homemaker, and her father, an emeritus professor of educational psychology at the University of Wales, was born in India to a Sikh family and moved to Britain in the 1960s. Last semester, Ms. Ghuman tried to teach her students by video link. This academic year, she is on an unpaid leave of absence.

“The arbitrary and inexplicable exclusion of Dr. Ghuman has been a personal tragedy for her and a cause of distress to Mills and to American higher education,” said Janet L. Holmgren, the president of Mills College, who called her “one of our most distinguished faculty members.”

“She seems to be in this limbo,” said Ms. Ghuman’s fiancé, Paul Flight, 47, who has visited her three times in Britain and is considering a move there. Mr. Flight, a countertenor, co-directed Darius Milhaud’s opera about Orpheus and Eurydice with Ms. Ghuman at Mills three years ago.

Ms. Ghuman’s descent into the bureaucratic netherworld began on Aug. 8, 2006, when she and Mr. Flight returned to San Francisco from a research trip to Britain. Armed immigration officers met them at the airplane door and escorted Ms. Ghuman away.

In a written account of the next eight hours that she prepared for her lawyer, Ms. Ghuman said that officers tore up her H-1B visa, which was valid through May 2008, defaced her British passport, and seemed suspicious of everything from her music cassettes to the fact that she had listed Welsh as a language she speaks. A redacted government report about the episode obtained by her lawyer under the Freedom of Information Act erroneously described her as “Hispanic.”