In the United States and around the world, it's becoming increasingly popular for police to fight prostitution by going after clients. This tack—often referred to as "the Nordic model"—is supposedly more progressive than targeting sex workers themselves.

A study published this week by medical journal BMJ explores how the criminalization of sex buyers affects the safety and working conditions of sex workers. Researchers from the University of British Columbia and the Gender and Sexual Health Initiative interviewed 31 street-based sex workers in Vancouver, Canada, where policies that criminalize clients were adopted by local law enforcement in January 2013.

While police "sustained a high level of visibility," they eased charging or arresting sex workers and showed increased concern for their safety, according to the interviews.

However, participants' accounts and police statistics indicated continued police enforcement of clients. This profoundly impacted the safety strategies sex workers employed. Sex workers continued to mistrust police, had to rush screening clients and were displaced to outlying areas with increased risks of violence, including being forced to engage in unprotected sex.

Whether cops are arresting sex buyers or sellers makes little difference—it still drives the practice underground and makes it more dangerous for those engaged. Researchers concluded that "criminalization and policing strategies that target clients reproduce the harms created by the criminalization of sex work, in particular, vulnerability to violence and HIV/STIs."

Targeting johns, buyers of sex, also increased the total number of sex-work-related arrests in Vancouver, from 47 in 2012 to 71 in 2013.

The BMJ study comes as Canada is debating whether to adopt the Nordic Model. In December 2013, the Canadian Supreme Court ruled that laws prohibiting brothels and prostitution were unconstitutional, giving the parliament 12 months to rewrite them. Canadian Justice Minister Peter MacKay is expected to release released a new prostitution bill today, patterned on practices in Sweden, Iceland, and Norway. In those countries, selling sexual services is legal but purchasing them is not.

It's not much of a model to emulate. "Evidence from Sweden, Norway, and now Vancouver confirms that criminalizing clients does not eliminate the sex industry but has a significant negative impact (on) sex workers," said University of Ottawa criminology professor Chris Bruckert.

Yet it's not just Canada looking to get Scandinavian with its sex work laws. Cities and states across the U.S.—including Boston, St. Louis, and New Jersey—have been planning and testing out similar strategies and touting it as progress.