Gura makes the point that current usage seems to have erroneously conflated "carry" with "concealed," such that anyone who mentions legal carry or permitted/licensed carry almost automatically and immediately jumps to "concealed carry." This is not the case. And there are faint hints at the distinction in the Heller decision, when Scalia discusses presumptively lawful restrictions.
Two states where this can be seen in operation today (among others, I'm sure) are Connecticut and Pennsylvania. Pennsylvania is an "open carry" state; except in the city of Philadelphia, open carry is legal without a license but a license is required for concealed carry. Within Philadelphia a license is required for open or concealed carry. On the PAFAO forum, there are regular reports of people who open carry being stopped and hassled by the police, both in and out of Philadelphia, because the police either don't know the law (usually the case outside of Philadelphia) or don't like the law (usually the case in Philadelphia). Often in PA police tell license holders that if they have a permit (in PA it is referred to in various parts of the law as both a license and a permit, furthering confusion) they MUST carry concealed. Which, of course, is not only wrong but also patently silly. ("You mean I can carry this hawgleg out in the open if'n I don't have a license, but if I git yer license I gotta conceal it? Is that whut yer a-tellin' me, Marshal Dillon?")
Connecticut, of the other hand, allows NO carry without a permit. But CT state law and the permit itself are silent regarding mode of carry. Thus, once someone has a CT carry permit, open carry is legal as well as concealed carry. Again, the police don't seem to like this and people have been arrested for open carry. The usual charge, since the police can't cite the carry law, is "disturbing the peace." These cases routinely get dismissed in court and the permit holder's permit is ordered restored, which makes the police even more unhappy because they claim the courts "aren't backing us up."
The situation in Ohio is perhaps the most instructive recent case that illustrates how this works. The Ohio state constitution includes a RKBA provision. Some years ago the Ohio supreme court ruled in a case that, because the state's constitution guarantees a right to bear arms, the State may not entirely prohibit doing so. Therefore, the court ruled, if the State wished to prohibit concealed carry (which Ohio had done, legislatively) the State could NOT prohibit open carry. Thus, Ohio became an "open carry" state. And the police were not happy. Activist citizens of Ohio began organizing open carry events, which made the police even more unhappy. Ultimately, several years ago the legislature either saw the light or caved in (depending on your point of view) and enacted concealed carry license legislation.
Al Norris, I believe, has commented on one of the western states (Utah, perhaps?) having done the same thing many years before.
So the legal premise is that the State may "regulate" the mode of bearing arms, but in the face of a constitutional guarantee of a RKBA the State may not prohibit the carrying of arms.
I don't remember which case, but I think in one of his briefs Gura made the point that a state could choose to allow concealed carry but prohibit open carry, or could choose to allow open carry while prohibiting concealed carry. Take your pick. (Most states seem to prefer concealed carry, since open carry -- they claim -- gets people upset.)