The First Amendment to the U.S. Constitution guarantees that any American can challenge the status quo and not be thrown in jail because of it. University professors enjoy an additional protection known as academic freedom. It allows them to write and speak about ideas that challenge the conventional wisdom without worrying that any controversial views will get them fired.

However, more and more professors are discovering that academic freedom is a tradition, not a constitutional guarantee. A few high-profile cases in recent weeks have captured the nation's attention, and they are causing concern on college campuses.

First, there was the case of Ward Churchill, an ethnic studies professor at the University of Colorado at Boulder. He had written in an essay that the civilians who died in the terrorist attacks of September 11th, 2001, were deserving of their fate. Professor Churchill and his family have received death threats because of that essay, and the governor of Colorado has called for him to be fired.

A second controversy involves Harvard University president Lawrence Summers, who suggested that biological differences may explain why more women are not in the fields of math and science. The comments provoked an outcry among Harvard's faculty, and Professor Summers soon found himself apologizing for the remarks.

A third debate concerns Columbia University's Middle Eastern Studies Department, which has been an ongoing concern for Jewish students. They are calling for the resignation of several prominent professors who have published papers highly critical of Israel's policies toward the Palestinians.

Cases such as this are dangerous because they undermine the very purpose of a university, according to Jonathan Knight, who directs the Program on Academic Freedom and Tenure for the American Association of University Professors. "We want to tolerate the freedom of the professors to teach and do research and write as they think right," says Mr. Knight, "because, in the end, what they do contributes so greatly to the betterment of our society."

Jonathan Knight says academic freedom does not guarantee that a professor will never lose his or her job. But he says it is a promise that a professor's research and ideas will not be judged by the changing winds of the political climate.

"It's not determined, in other words, by pressure groups outside the institution," he says. "It's not determined by state legislators. It's not determined by governors of states. It must be determined by those who have the long training and experience to assess whether an individual faculty member has strayed egregiously from the path."

Increasingly, however, lawmakers, students, and members of the general public are insisting that they have the right to determine whether a faculty member stays or goes.

The Internet may have a lot to do with this development. Jon Wiener, a history professor at the University of California at Irvine, says the worldwide web has given people an expansive forum where they can complain about professors and, sometimes, quote them out of context. In his latest book, Historians in Trouble, Professor Wiener considers the cases of 12 professors who recently had their professional research and conduct scrutinized by the public.

"Some of those people lost their jobs?some of those people received high honors from the Bush White House?and some of those people were ignored, even though there are a lot of similarities in the misconduct they were charged with," he says. "What I found is that the crucial factor in determining who gets into trouble and who gets punished is not the seriousness of the charges against them, but rather the political context."

Jon Wiener argues that conservatives have been far more aggressive than liberals in their attacks on academia. However, conservative commentator David Horowitz says that is because liberal professors dominate America's academic establishment.

"The real problem is that the greatest threat to academic freedom today is the professors," says Mr. Horowitz, who manages the website, "They have virtually excluded from their faculties anybody who is not a left-winger or a liberal. Libertarians and conservatives and religious people are as rare as unicorns on most American faculties. And the situation is getting worse, not better."

David Horowitz points to the case involving Harvard's Lawrence Summers as an example of liberal dominance in academia. He notes that it was professors who were outraged by Mr. Summers' comments on women and science.

But Jon Wiener of U.C. Irvine says the professors were not concerned because Lawrence Summers had put forth a controversial idea. It was that, unlike the Middle Eastern Studies professors at Columbia who have criticized Israel, President Summers was speaking outside his realm of expertise.

"Lawrence Summers was not saying that women are innately inferior to men in science as part of his scholarly research," Professor Wiener says. "He knows nothing about this subject. He's trained as an economist. He was saying this as the leader of the institution, trying to explain the failure of Harvard to have very many women in the senior ranks of its science fields."

A proposal within Harvard's faculty to issue a vote of no confidence against their president has been put aside, at least for now. Meanwhile. Ward Churchill's fate in Colorado is still undetermined. And Rashid Khalidi, one of the professors at Columbia whose comments about Israel have generated controversy, was recently dismissed by New York City's Department of Education, which had hired him to lead a course for public school teachers on how to talk to their students about Middle Eastern politics.