A shopping mall is private property. If it's posted "no concealed carry" or you're otherwise informed concealed carry is prohibited, then you cannot legally carry there and you are trespassing if you carry in spite of the notification. Same as if it's not posted and you're carrying - someone in charge of the property finds out you're carrying and informs you it's prohibited. If they then ask you to leave, you must comply or you are trespassing.
Any government building (excluding federal property) - for example Lakewood City Hall - cannot prohibit concealed carry unless they have security personnel and electronic screening devices permanently posted at each entrance. The statute is very clear on that. They can put up all the signs they want but unless they have personnel and equipment in place and actually screen for weapons, they're not in compliance with the law.
There's no state standard on signage (for example like there is in Texas) or notification that a specific location prohibits concealed carry.