Six months after Washington state legislators passed one of the most sweeping underage sex trafficking laws in the country—a law that required internet sites operating in the state to document that advertised escorts were at least 18—the state has apparently agreed with a federal judge that the law is unconstitutional and has dropped its defense.

Attorney General Rob McKenna's office hasn't returned my calls for comment. However, is a big win for backpage.com, which promptly challenged the new law back in June.

US District Court Judge Ricardo S. Martinez's final judgement (.pdf) states that the state's sex trafficking law violates both the First and 14th Amendments, and steamrolls over the federal Communications Decency Act and sections of the Commerce Clause.

"Threatening to throw service providers in jail for what their users say or do is misguided, incredibly harmful to online free expression generally, and violates federal law," said attorney Matt Zimmerman, who represented a second plaintiff, the Electronic Frontier Foundation, in the case. "We are grateful that the state of Washington has agreed that this statute cannot and will not be enforced against the Internet Archive or anyone else."

"The law is unconstitutionally vague," Judge Martinez concluded. He also called the law "overbroad" and "not narrowly tailored to the state's asserted governmental interests," and ordered the state to pay plaintiffs' attorneys' fees to the tune of $200,000.

Thanks to Slog tipper Matt.