How is it that a sign is going to stop someone from committing a crime?  Doesn't the fact that they show up at a state building with a firearm planning to hurt someone pretty much rule out the possibility of them stopping because it's against the law?

Meanwhile, concealed carry permit holders who have passed state and federal background checks are now made to either leave their homes unarmed, or handle their firearms unnecessarily in the parking lot as they leave their firearm in the car, unatttended?

Maybe you should also put a sign in the parking lot telling people it's illegal to steal.  That way none of these law-abiding citizens' guns get stolen.