So I'll admit that I'm no expert, I'm just playing devils advocate here.A key could be the definition of regulate.
Websters defines it as
: to bring under the control of law or constituted authority (2) : to make regulations for or concerning <regulate the industries of a country>
So it would seem that the intent could be that political subdivision can't enact their own rules concerning the ownership, possession, carrying, transportation, registration, transfer, and storage of firearms, ammunition, and firearm accessories. The argument might be made that the PD wasn't regulating, based on this definition of regulate. Essentially they would say they have no local rule (provision of an ordinance, measure, enactment, rule, or policy) they were enforcing, thus they were not regulating anything.
I don't know the case law, so there might already be clarification regarding any type of suggestions being made. Context of the suggestion would seem to be important (e.g. I suggest you do this if you don't want trouble vs. hey you might just cover it up until people settle down.) I don't see where the 2nd example is prohibited. It would be easy to argue that it's non of their business, but violating law maybe different.
Just presenting another view point, it will be interesting to see the outcome.
Determining the mode of carry wouldn't be considered "regulating" to you?