Right, I thought that might be what you were referring to. This is where we get into weeds technically:

Those regulations apply to active jamming, which is the use of an electronic device(s) to emit signals that interfere with lawfully approved channels. It is important to note that this holds no practical bearing upon structures as they by definition cannot engage in active jamming, only in passive blocking or coincidental interference.

What’s being experienced with Walmart’s lack of 5G is likely due to the fact that 5G does not penetrate walls very well. Combine this with the fact that you have hundreds of devices in the same enclosed space trying to talk to the same tower some miles away on the lower bandwidth 5G channel that can penetrate walls, and you can see how 5G access is effectively being “denied” simply by the nature of the business. Walmart could implement an on-premises 5G relay to solve the issue, but why would they want to take on that tech debt? All they are required to do by law is make sure E911 is not impeded by the building or operations of the business. They don’t owe you access to other radio waves when on their premises.

If this regulation were to somehow be applied to passive blocking like what I’ve described, then Faraday cages would be illegal-- which aren’t, again as long as E911 is not impeded. This would also make high security bamk vaults illegal due to the thick wall construction.