Firearms regulation is mostly left to the states in this country. Every single one of them except Illinois permits carrying a concealed weapon, mostly but not always with a license. You have to be at least 23 years old, take an approved training course and pay $100 but otherwise it's not too hard to get one in Missouri. Somebody could walk into my office packing heat. I'm sure it's happened. There are some exceptions. You can't carry a concealed handgun in a prison (that's a relief), bars (except the owner), publicly accessible hospitals (does that mean it's okay in a locked psych ward?), casinos (I said hit me!) or any church (amen, brother). Plus a few other places.
The gentlemen above were answering questions and selling merchandise for this trade at the Gyppy Caravan. Note the hunter-orange Cardinals cap and the tee shirt from the National Rifle Association convention that was here in April. The flea market booth below was run by a very friendly family selling toy wooden assault weapons. Buy one and get a pistol at half price.