Check a little deeper in to the physical requirements for the no firearms sign. Here's why.
In Texas, we have a very clear definition of the details of the sign. It has to be a certain size and have the exact wording prescribed by law. In other words, a Post-It note in pencil stuck on a window 6 feet from the entry door isn't sufficient. And a banner with 2 foot tall letters on an awning visible from a block away isn't sufficient either. The wording, font, size, color, and location of the sign is prescribed by Texas law. Intent to prohibit is not sufficient. The business owner must obtain and post the notice properly. A post-it note or index card won't cut it.
In Texas, some businesses try to have it both ways, with some success I think. The business owners will post a non-official sign that looks official enough for most people to think they are entering a no-carry zone, but most licensed-to-carry people see the sign does not meet the requirements and can choose to ignore the sign from a legal standpoint, IF the permit holder is carrying concealed. Everyone is happy, at least until one side or the other challenges the signage and presses the owner either to post the proper sign or take down the non-conforming one.
Joe
Joe