The U.S. District Court of Western Washington has just put an item on Congress’ to-do list: Stop providing legal cover for child prostitution.

Congress didn’t set out to empower pimps when it approved the Communications Decency Act of 1996. But it failed to anticipate how skillfully they would exploit the Internet through Backpage.com and other prostitution-friendly websites.

An important provision in the act was intended to protect legitimate Internet websites from legal action arising from information posted by third parties. A newspaper, for example, could not be sued or prosecuted over malicious comments posted by readers on its articles.

But there was an unintended consequence: The law is now effectively enabling the sex-trafficking of young girls.

Until Thursday, Washington had the toughest anti-child-prostitution law in the nation, Engrossed Senate Bill 6251. It aimed straight at the online nexus of the industry: Any website that opted to run ads for sex services – that would be you, Backpage.com – would be required to verify that the girls in the photos were at least 18.

If it did not so verify, the people who run the site could face felony prosecution and civil lawsuits.

Federal Judge Ricardo Martinez on Thursday struck down the Washington law, partially on grounds that it violated the Communications Decency Act.

We don’t like the decision, but it’s probably a reasonable reading of a law that was written before anyone knew how much the Internet would extend the reach of predators.

Any website that hosts prostitution ads will wind up being used to sell adolescent girls. If such a website attracts lots of people, it will inevitably help sell lots of girls.

Backpage.com often plays a role in Puget Sound child-trafficking.

A month ago, for example, two Pierce County men indicted on charges of pimping out juvenile girls from Puyallup and Tacoma. The case broke when a police officer outside found a 16-year-old from Puyallup in a motel outside Los Angeles; she had been beaten and choked for refusing to sell herself that day.

How were the girls sold? Backpage.com.

Congress can surely figure out a way to fine-tune the federal law so that it protects legitimate information brokers without protecting companies that are effectively complicit with criminals.

In this country, all pimps are criminals, whether they sell children or not. There’s something indecent about a “decency act” that helps them ply this vicious trade.