In some areas of the world and in history, I think it is illegal for men to expose their chest also, on the flipside, there are numerous tribes who view total nudity from both sexes as the norm. A society's acceptance, or not, of nudity in any shape or form is clearly a subjective cultural phenomenon. I feel lucky that I have lived in more than one country in my life, having lived in Switzerland and now the UK, and indeed, there is a large difference in tollerance. It is possible things have changed since I lived there, but as I recall nudity out of context (as in public for little or no good relevant reason) was "fround upon" as apposed to outright illegal, as it is in the UK (female breasts and/or genitals of either sex cannot be exposed in public except where licenced etc).
Given the subjectivity on nudity and its appropriate context, it is difficult to accurately place a label of right or wrong. Myself I was raised around nudist camps, so to me a body is a body is a body, its what you DO with that body that makes it sexual. A naked body in and of itself, does not actually strike me as sexual, whilst a fully clothed person, saying the right things or moving the right way, is increadibly sexual. Sadly people seem to label the body as the source of all sexuality, which isn't the case at all, sexuality is as much psychological as it is physical, perhaps even more so.
I think that a woman exposing her breasts in public should not be "illegal", for I do not believe there is a point in making something non-threatening illgeal. Murder is threatening, theft is threatening, rape is threatening, as such, they are, & should, be illegal, I fail to see what harm the sight of a woman's breast will do anyone, for it is merely a cultural paradigm anyway.
Having said that however, I do not think it good manners to just prance around willy nilly with one's breasts out, anymore than it is for a man to prance around with his penis hanging out, some people find it vulgar, and it isn't fair to just ignore the emotions of everyone else just because you feel like it. There is a time and a place for everything.
So my conclusion is that it ought not to be a legal issue but rather an issue of appropriate politeness, and to be put in the same catgory as swearing out of context (as an example). It is not illegal to swear, and it shouldn't be, its just bad manners.:cool: