SEATTLE -- Seattle Parks and Recreation on Wednesday put into effect a new rule banning the possession or display of firearms at playgrounds, community centers and other places where children are likely to be.

"When children and families visit a Seattle Parks and Recreation pool, playground, community center or other facility, they are entitled to a reasonable expectation of safety," Mayor Greg Nickels said in a statement. "It's common sense to prohibit guns in places where kids and young adults play and learn."

But State Attorney General Rob McKenna said the ban won't stand if challenged in court. McKenna has previously said cities can't pass gun ban laws.

The new rule calls for the ban to take effect at designated facilities once signs are posted. The first signs are to be posted Friday, with the rest up by Dec. 1.

In all, the rule will be applied at more than 500 parks, recreation centers, pools, beaches and golf courses.

The ban won't include the Seattle Center, even though it was last year's shooting at Folklife that prompted the new policy.

The Seattle Center isn't included is because it's not run by the parks department.