It would be easier to ask which countries is it illegal in, that would be a very short list, with mainly the U.S. were consenting adult sexual rights are denied.
Prostitution is LEGAL (with some restrictions that aren't that bad) in Canada, most all of Europe including England, France, Wales, Denmark, etc., most of South America including most of Mexico (often in special zones), Brazil, Israel (Tel Aviv known as the brothel capital of the world), Australia, and many other countries. It is either legal or very tolerated in most all of Asia and even Iran has "temporary wives" which can be for only a few hours! New Zealand passed in 2003 one of the most comprehensive decriminalization acts which even made street hookers legal which is causing many concerns. I do NOT support public nuisance street hookers being legal unless in special zones. But PRIVATE consenting adult sexwork should be legal as it is in most of the world except the U.S.
As long as prostitution is kept illegal, and women are persecuted for acts which harm no one, prostitute women will be subject to brutality at the hands of misogynists and moralists -- they are, arguably, the same group. And when prostitutes are treated as second class citizens, and in extreme cases, as less than human, then all women who dare to step out of their social constructs will be labeled as whores and treated accordingly. For these reasons, the rights of all women are contingent upon the rights accorded to the most vulnerable women. - From Dr. Jocelyn Elders: March 1997 International Prostitution Conference highlights: Keynote speaker was Dr. Jocelyn Elders. Elders was surgeon general until President. Clinton fired her for supporting masturbation. Elders called for prostitution to be decriminalized. Dr. Elders has also said: "We say that [hookers] are selling their bodies, but how is that different from athletes? They're selling their bodies. Models? They're selling their bodies. Actors? They're selling their bodies." See http://www.lpt.com/