The free marketplace of ideas that you and I know as today's Internet might have been an entirely different thing if Congress had gotten its way in the 1990s.

The Communications Decency Act, passed in 1996, prohibited the publication of anything "obscene or indecent" on the Internet where children could access it. It was a vague and overreaching standard and the ACLU challenged it as soon as it was signed into law.

Your Constitutional Rights: Reno v. ACLU (a one-minute podcast)

The ACLU won in District Court but the federal government appealed. In 1997, Reno v. ACLU was the first Internet case to appear before the Supreme Court.

Attorney General Janet Reno argued we must protect minors from harmful material that is "indecent" and "patently offensive."

Fifteen years ago today, the Supreme Court ruled for the ACLU. "Vague, undefined terms" says a unanimous Court. "Notwithstanding the legitimacy and importance of the congressional goal of protecting children from harmful materials, we agree with the three judge District Court that the statute abridges 'the freedom of speech' protected by the First Amendment."

In short, the Communications Decency Act would have prevented adults from distributing and receiving information they were entitled to receive.

"The general,undefined terms 'indecent' and 'patently offensive' cover large amounts of nonpornographic material with serious educational or other value..."  wrote Justice Paul Stevens. "The vagueness of such a content based regulation, coupled with its increased deterrent effect as a criminal statute, raise special First Amendment concerns because of its obvious chilling effect on free speech."

Without this ruling the Internet would be a far different place.