Lawrence Lessig--a prominent expert on Internet law who advised the judge in the recent Microsoft antitrust trial--announced last week that he will leave his post as Berkman Professor of Entrepreneurial Legal Studies at Harvard Law School to accept a tenured professorship at Stanford Law School.

His decision to leave Harvard Law School (HLS) strikes a blow to the school, which has watched Stanford develop a reputation of being on the cutting edge of the study of the Internet and technology.

"The loss is incalculable--he is the premier cyberlaw scholar in the country," said Climenko Professor of Law Charles J. Ogletree, one of Lessig's colleagues.

Lessig, who has been on leave for this academic year, was out of the country yesterday. But he wrote in an e-mail message that he decided to accept a position at Stanford in order to be closer to his wife.

"I was married in July, and it was important to my wife to be in San

Francisco," he wrote. "So Harvard hasn't changed: it is as it was--an extraordinary law school. The change is all in my life."

Lessig said the recent U.S. News and World Report rankings of law schools, which ranked Harvard's law school behind Stanford's, did not influence his decision. And he said Harvard is the leader in study of public policy as it relates to new technologies.

"I think Harvard is miles ahead of the competition right now. The Berkman Center is the leading law policy center for technology issues in the world," he said.

Some of his colleagues said Lessig's departure is a great loss to the school.

"We are sorry to see Lessig leave HLS," said Assistant Dean of Academic Affairs Stephen A. Ray. "He has been a strong contributor to our curriculum."

In previous semesters, Lessig has taught a range of courses, some of which--like "The High-Tech Entrepreneur"--have focused primarily on Internet and software law.

He has also served as a fellow of the Berkman Center for Internet and Society --a research institute on cyberspace and its development.

According to Ogletree, Lessig has played an "integral" role in the program.

Lessig's announcement comes less than a month after a ruling in the Microsoft antitrust lawsuit that found the software company guilty of anti-competitive behavior. In that case, Lessig had advised Judge Thomas Penfield Jackson that Microsoft's policy of "tying" its web browser with its Windows operating system may have given the company an unfair advantage over its competitors.

His role as a friend of the court in the Microsoft case brought publicity to the center and to HLS.

Lessig supported the government's contention that regulation was necessary because "tying" or bundling the Windows operating system with Internet Explorer restricted the freedom of the user to choose his or her own browser.

"The choice is not between regulation and no regulation," wrote Lessig in a recent article in The American Prospect. "The choice is whether we architect the network to give power to network owners to regulate innovation, or whether we architect it to remove that power to regulate."

In addition to his role in the Microsoft case, Lessig recently published a well-reviewed book, Code and Other Laws of Cyberspace.

Ogletree said that Lessig enjoyed his teaching responsibilities at Harvard but found it increasingly difficult to teach on the East Coast and spend time with his wife.

"He really struggled with this," said Ogletree.

Lessig's Stanford appointment, according to the Stanford Law School website, is pending formal approval by the university's Advisory Board and president