Interesting observation. While the 2ndA is a prohibition against such regulation (see prior post), insofar as the infringement occurs it may be regulated for uniformity.
As the tired old analogy that free speech doesn't give one the right to shout 'fire!' in a crowded theater means that free speech can be regulated, for better or worse (worse IMHO) the Supreme Court ruled in Heller v DC that the 2nd Amendment is not an 'absolute' right and can also be regulated.
Likewise, the manner in which the 2nd Amendment is exercised can also be regulated, both with regards to concealment and with regards to what sort of weapon may be kept and borne.