The law says no carry in "sensitive" areas - places where prisoners are routinely kept/found. This means that while the lobby area is OK, there may be some difficulty with offices and corridors as well as the more obvious prisoner holding areas.
Generally those areas are marked so that LEOs do not inadverdantly bring a firearm into an area where some bad guy could take it away from them and use it to effect an escape. (And why, you ask, do LEOs need a sign reminding them where not to bring guns? Wait for it -- because someone once
did bring a gun there!:shocker
The location of the Magistrate's ofice should have nothing to do with the sign that seemingly places the entire area "off limits" to guns, knives or other weapons.*
Politely ask them to remove the sign - maybe even use one of those e-cards Ed likes to use which makes it easy to post here. Let us know what happens.
stay safe.
*What is up with that "knives, guns or other weapons" bit that LEOs seem to just love to use? Why can't/don't they just go with the generic "weapons"? They seem to be just as afraid of bazookas, thermonuclear bombs and outer space death rays as they are guns and knives, so why mention thosre two and then lump everything else together?