Let's walk through a simple exercise in economic theory:

1. Demand exists for paid sex.

2. The legal supply of sex-for-sale is nonexistent in states where prostitution is outlawed, including Florida.

Ergo, some folks conclude, Florida should legalize prostitution to stem the tide of illegal sex trafficking.

I've seen and heard this argument all over the place in the aftermath of the massage parlor and human-trafficking investigation that resulted in the arrest of nearly 300 suspected "johns," including New England Patriots owner Robert Kraft.

The argument isn't coming from fringe-of-society anarchists (though they might agree). One of the most visible proponents has been a retired St. Lucie County judge, Cliff Barnes. Ever since the alleged sex-spa busts, he's been advocating on Facebook for legalization, taxation and regulation of prostitution.

So I called him to talk about it.

“We cannot afford to chase people around who do things that we think are harmful to themselves,” Barnes said. “If we had unlimited funds, we could go after every tiny societal problem.”

We don't, so he advocates a more pragmatic approach.

“I think government, ideally, ought to be in the business of educating adults, taxing the use of things that harm an adult body, and using the money that’s derived from taxing it for education and treatment,” Barnes said.

If, right about now, you’re thinking this simple economic exercise isn’t so simple, I'm right there with you.

Sex trafficking is a complex issue

The product we’re talking about is not pot or pills; it’s human bodies. And where selling bodies is involved, opportunity looms large for exploitation and abuse.

Don't take my word for it. Plenty of researchers have delved into the effects of legalized prostitution on human trafficking.

A 2012 study titled “Does Legalized Prostitution Increase Human Trafficking?” published in the journal World Development examined data from 116 countries and case studies from Denmark, Germany and Switzerland. The researchers found countries with legalized prostitution are associated with higher inflows of human trafficking than countries where prostitution is prohibited.

Why? Because the “scale effect” of legalized prostitution — meaning expansion of the market — outweighs the “substitution effect” in which legal workers are used instead of illegal workers.

The problem of human trafficking was greater in high-income countries because of the purchasing power of clients, according to the study (conducted by researchers from the London School of Economics, the German Institute for Economic Research and the University of Heidelberg).

But — and, yes, there's a “but” — those researchers and others found benefits to legalizing prostitution, too.

What about working conditions, disease?

Chief among the benefits:

“Working conditions could be substantially improved for prostitutes — at least those legally employed — if prostitution is legalized,” wrote the authors of the World Development study.

Then there’s the disease factor.

A separate study, examining a period of legalized indoor prostitution in Rhode Island (from 2003 to 2009), found cases of gonorrhea in women declined 40 percent. Reported rape offenses declined 30 percent when prostitution was decriminalized there. We can't be certain if legal prostitution led to the decline, but the correlation exists.

Last month, a pair of New York lawmakers proposed decriminalizing all sex work in the Empire State.

"Criminalization exposes people to exploitation," the state senators wrote in an op-ed in the New York Daily News. "Prostitution records take people’s choices away, and when people have no choice but to trade sex to survive, they are more likely to be trafficked."

For Barnes, who was a county commissioner before he became a judge, the debate also intersects with taxes and prison policy. As a county commissioner, he dealt with the burdensome costs of running a jail and a sheriff's department.

“If you legalize the act of prostitution, then you can free up resources to attack the traffickers and the pimps,” he said.

Barnes believes the private prison industry incentivizes locking people up for lower-level offenses such as prostitution.

“There are people who profit off chasing marijuana users and prostitutes and johns around,” Barnes said. “There are private prisons, and they want to fill them.”

Still. Is that good enough reason to make prostitution a legal gig?

I can’t stop thinking about the apparent victims revealed as a result of the Feb. 19 raid of 10 spas in Florida.

More: Florida's human trafficking and massage parlor busts: The full story

More: Sex trafficking is in plain sight but invisible

Investigators say the women, originally from China, were being held against their will by spa operators tied to an international human-trafficking ring. (One suspect has been charged with human trafficking, according to Vero Beach Police — but prosecutors have yet to formally file that charge, and it's unclear whether it will materialize.)

If research indicates legalizing prostitution increases the odds of this kind of exploitation, why would we entertain the idea?

Then there’s the question of decency.

Should a civilized society have standards for it? Does legalized prostitution violate such standards?

For Barnes, it doesn’t.

“As long as they’re not harming other people," he said. "That’s where you draw the line.”

I'm not so certain.

Does legalized prostitution inevitably lead to more people being harmed? There's a case to be made that it does — at least when we're talking about human trafficking.

We can go round and round about the pros and cons, but let's be honest: This debate is moot in Florida.

There's no way in Hades the conservative state Legislature would embrace legalizing prostitution. If anything, Florida lawmakers are moving the opposite direction. They have filed legislation calling for mandatory jail time for “johns” in human trafficking cases.

Martin County Sheriff William Snyder, whose agency launched the sex spa investigation, wants harsh sentences for all of the 300 or so men charged with soliciting prostitution. The maximum sentence for the misdemeanor charge is 60 days to a year in jail, though actual sentences are typically far less.

“If we don’t stop the demand,” Snyder said, “law enforcement in the United States does not have the capacity to stop the sex-trafficking trade.”

In the months to come, "johns" including Kraft will head to court to fight charges or accept plea deals. We will know their fates relatively soon.

It will be years, however, before we know if Florida's salacious sex-spa bust of 2019 put a dent in human trafficking.

Eve Samples is opinion and audience engagement editor for TCPalm/Treasure Coast Newspapers, which is part of the USA TODAY Network. Contact her at eve.samples@tcpalm.com or @EveSamples on Twitter.