Major League Baseball is making it clear to players as they arrive to camp: Keep guns out of the clubhouse. Signs are posted in locker rooms stating "individuals are prohibited from possessing deadly weapons while performing any services for MLB."

The rule applied last season, but signs were not posted.

"The commissioner's office negotiated the policy with the union, as it applies to players," players' association head Michael Weiner said. "The content of the notice itself was not agreed to by the union."

The rules were adopted after former New York Giants receiver Plaxico Burress accidentally shot himself at a nightclub. And last month, NBA commissioner David Stern suspended Washington Wizards star Gilbert Arenas after he brought guns to the Verizon Center.

By Scott Boeck