That's true. If you don't abide by it you're a criminal.
Do the CC guys carry where a business says not to?
State dependent, MOST "no guns allowed" signs do not comply with state regulations or lack force of law.
Tbise signs aren't worth the paper they're printed on, and carry as much weight as the cranky old codger waving a 20mph sign on a 40mph street because he doesn't like traffic noise.
For example, below are the requirements for Tennessee. I encourage anyone to educate themselves on the specifics of the law in their state so they know which (if any) signs carry force of law, and which signs can be simply ignored.
A. Permit Holders
In order to prohibit firearms on the premises, the notice of such prohibition must be posted in the form of a sign.Tennessee gives individuals, corporations, business entities, and local, state, and federal government entities or agents thereof the authority to prohibit firearm possession on their premises.
No Guns signs must meet all requirements to prohibit firearms on that premises. The requirements are:
The sign must be displayed in prominent locations including all entrances primarily used by persons entering the property, building, or portion of the property where weapon possession is prohibited.
The notice must be plainly visible to the average person.
The notice must be posted in English, but may include a duplicate notice in any other language used by individuals frequenting the premises.
The sign shall include the phrase “NO FIREARMS ALLOWED” and such phrase must measure one inch high and eight inches wide; the sign must also include the phrase “As authorized by T.C.A. § 39-17-1359.”
The sign must also include a pictorial representation of the phrase “NO FIREARMS ALLOWED” in the form of a circle with a diagonal line through the circle and the image of a firearm inside the circle under the diagonal line. The diagonal line shall be at a forty-five degree angle from the upper left to the lower right side of the circle.