The guidelines are the first of its kind among the four major North American professional sports leagues (MLB, NFL, NBA, NHL) and implements a standard of dress for media members. It is an attempt to maintain a level of professionalism during the hot summer months when clothes have a tendency to get skimpier.
Members of the media will be prohibited from wearing flip-flops, short skirts, tank tops or anything with a team logo.
"This is not in response to any single incident," MLB spokesman Pat Courtney told The Associated Press. "It can be a fine line. What one person views as appropriate may not be seen the same way by someone else."
According to the guidelines, members of the media should dress "in an appropriate and professional manner." Clothing should be proper for a "business-casual work environment" when in clubhouses, press boxes and on fields.
Ripped jeans, visible undergarments, sheer clothing, one-shouldered and strapless shirts or clothing exposing bare midriffs will be banned. Skirts, dresses or shorts cut more than three or four inches above the knee will be deemed to be in violation.
"We just thought it was time to get a little organized, to put it in place before there was an incident," said Phyllis Merhige, an MLB senior vice president.
"There's no one who expects reporters to wear a suit and tie. But with the advent of different media, there are now individuals who are not part of a bigger organization that may have a dress code."
San Francisco Chronicle writer Susan Slusser, who was recently elected vice president of the Baseball Writers' Association of America and served as a member of the guidelines panel said, "I believe the baseball media in general could dress slightly more professionally."
MLB said action would be considered if the guidelines were broken.
"I remember the old days, when even the people in Triple-A would wear a coat and tie," former Marlins manager Jack McKeon told the AP. "Now, it's casual. Less than casual, really."
Matt Weber is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.