The International Olympic Committee is barring competitors, as well as coaches, support personnel and other officials, from writing firsthand accounts for news and other Web sites.
An exception is if an athlete has a personal Web site that they did not set up specifically for the Games.
The IOC's rationale for the restrictions is that athletes and their coaches should not serve as journalists - and that the interests of broadcast rights-holders and accredited media come first.
Participants in the games may respond to written questions from reporters or participate in online chat sessions - akin to a face-to-face or telephone interview - but they may not post journals or online diaries, blogs in Internet parlance, until the Games end Aug. 29.
To protect lucrative broadcast contracts, athletes and other participants are also prohibited from posting any video, audio or still photos they take themselves, even after the games, unless they get permission ahead of time. (Photos taken by accredited journalists are allowed on the personal sites.)
The editor of a Web site that had arranged athlete diaries called the restrictions shortsighted.
"This is unfathomable to me," said Robert Bliwise, editor of Duke Magazine, Duke University's alumni publication. "I don't understand what the International Olympic Committee might be concerned about. It's a way to engage a wide audience with reporting from the field and therefore generate excitement and interest in the games."
His site had made arrangements with two graduates, pole vaulter Jillian Schwartz and race walker Curt Clausen, to provide firsthand accounts for the university's alumni.
"This is a means to personalize the Olympics, to excite a constituency with the thrill that comes with the knowledge that a couple of their own are participants in the competition," Bliwise said.
One entry, from Schwartz, remained posted Thursday; Bliwise said he had yet to be formally informed of any violations.
But an IOC official, speaking on condition of anonymity, said third-party sites like Duke's are covered by the restrictions.
The Olympic guidelines threaten to yank credentials from athletes who are in violation as well as to impose other sanctions or take legal action for any monetary damages.
But the official said the IOC has yet to take any action against an athlete.
The IOC distributed the policies to each country's Olympic committee in February.
By Anick Jesdanun