Let me try and clarify MS law and AG opinion on your circumstance. As stated in the MS Constitution the legislature can only regulate concealed carry. They have no authority to regulate open carry so the MS code you referenced only refers to carrying a concealed weapon, not open carry.
In MS you must make a distinction between gun laws and trespass law. The AG has stated several times that any "No Gun" sign is sufficient warning for trespass and the statutory language referenced in MS Code 45-9-101 is unnecessary (for almost all circumstances). Let me provide an example that may explain.
1. Let's say you unwittingly (or willingly) open carry into a store with a "No Guns" sign. You have violated no firearms law. However, you could theoretically be in violation of trespass law (MS Code 97-17-97) as you were given notice by a sign that firearms weren't allowed. In reality you most likely will never be arrested for trespass unless you have been previously warned by law enforcement not to enter with a firearm, yet continue to do so.
Most people don't understand the minutia of the laws and that includes law enforcement unfortunately, and store owners especially. Their sign referencing MS Code 45-9-101 could only, maybe, possibly, put in jeopardy a standard MS Firearms permit holder to be in violation of 45-9-101. That sign would not trigger a firearms violation for an open carrier or MS enhanced carry endorsement holder. Theoretically it could trigger a trespass violation though. Theoretically.