Understanding the scope, harms and public health implications of policies addressing the world's oldest profession is really tricky. While prostitution - the buying and selling of sex - is a multibillion dollar industry, the sex trade is clandestine by nature. It's taboo. That makes it really hard to study, especially in the United States.

That's most often the case, except in this one part of the country, where the laws of prostitution were totally upended. It's a peculiar story that's largely left out of the current discussion. The place in question is not Nevada, where there's a small number of regulated brothels in certain rural counties.

It's a whole state - Rhode Island.

For several years, ending in 2009, indoor prostitution such as in massage parlors, strip clubs and through online escorts, was not a crime in this tiny New England State.

The whole thing happened somewhat unintentionally. But at the time, it fueled a heated public debate about sex, crime and health.

Years later, some are revisiting the lessons learned.