Posted this elsewhere: If you come across a mall, store, or office building with a restriction for concealed carry, send them a letter or email. The one I've used asks who my family contacts if I'm injured or killed when unable to defend myself. And that our lawyer has been told to start at $10 million and work up. Local chain had an apology back to me in under 36 hours; the signs came down, but they don't let employees carry. Understand that I wasn't the only one who went after them. My employer of 20+ years will fire you if you have a firearm locked in a box in the trunk of your car in the company parking lot or at a company-sponsored event. We've been told it's part of our employment contract. (And a co-worker was patted down, his cubicle stripped, and his car opened and turned out when a guard saw a set of hearing "muffs" in his car. No weapon, but he was warned about termination, anyway. I was threatened with termination for discussing a day at the range. Now I'm retired and won't step foot in any of our offices.

I've seen several people comment that that sign has no legal force (In Utah).

There's no provision for forbidding concealed weapons, so that demand is really a request, one that doesn't carry the force of law behind it.

But, even if it did, wouldn't the fabled HR 218 supercede it?

The law says that if it is posted, and you have a weapon, you can be asked to leave. If you do not comply, you can be arrested for trespassing.