I'm not writing the name of your store, because I don't want to leave you vulnerable. You'll understand why in just a moment.
I am writing to let you know that the Anti-Gun Barrier installed in your store has malfunctioned. With my firearm legally concealed in my waistband, I accidentally walked into your store. The sign you put up to warn me that you had installed an Anti-Gun Barrier was obscured from my vision by the summer themed display of hay bales, potted plants, and a large sign denoting some sale price. You should think about being a little more careful with the placement of such displays, so that when the energy shield is working again gun owners will be spared the embarrassment getting hung up in the invisible, selectively permeable wall created by the Anti-Gun Barrier. Someone could rip their pants.
I concluded, therefore, that your Anti-Gun Barrier is not working. I know how hard it is to tell if those things are working, what with the fact that the energy shield is completely invisible and there is absolutely no "hum" from the generator.
It is my sincerest hope that you can fix the problem with little difficulty. Check the amorphous gemstones first, they can easily get out of alignment.
I hope I'm not writing this letter in vain, and it is just a malfunction. It's not like you would put up signs pretending you had an Anti-Gun Barrier and expect that to protect you. That would just be silly, wouldn't it. Sorry to even bring it up.
Because I must,
Jesse Riggs, concerned shopper
"That shield is certainly putting a crimp in my day."―Obi-Wan Kenobi during the Battle of Christophsis
Addendum: According to Missouri law, it is not a crime to carry a concealed weapon into a business displaying "No Gun" signs. It becomes a crime only if the individual carrying is asked to leave and refuses.