FWIW Seattle Center claims special rights over firearms if you read their policy at http://seattlecenter.com/about/rules.aspxCC into the pacific science center, OC on the way out. OC at the sausage festival and OC at Seattle center. No problems.
"4. Weapons. It is Prohibited To....
Carry concealed or unconcealed on his or her person any dangerous knife unless used as a tool for work by Seattle Center employees or their authorized agents, or carry concealed on his or her person any weapon. Seattle Center employees are subject to the Seattle Center Employees Firearm Policy.
Possess or display a firearm on the campus, unless permitted by applicable law."
Note that a concealed weapon would technically count under the 'carry concealed on his or her person any weapon' clause because they include firearms in the definition of weapons, even if you had an out under the following 'permitted by applicable law' clause.
Of course, all of this is void under pre-emption, but just FYI. Anyone care to try and get it clarified?