Ashcroft v. American Civil Liberties Union, 535 U.S. 564 (2002), followed by 542 U.S. 656 (2004), was a decision of the United States Supreme Court, ruling that the Child Online Protection Act (COPA) was unconstitutional as a violation of the First Amendment's guarantee of freedom of speech.

Material that is "harmful to minors" was defined as: any communication, picture, image, graphic image file, article, recording, writing, or other matter of any kind that is obscene or that— Thus, COPA was narrower and more precise than the CDA because it attempted to make use of the Miller Test to find "obscene" internet material that could be regulated.

Justice Anthony Kennedy, who delivered the majority opinion, suggested that parents and educators could voluntarily adopt Internet filters and related software to reduce the visibility of harmful or unwanted material.

... [T]he Government failed to introduce specific evidence proving that existing filtering technologies are less effective than the restrictions in COPA.”[11] The court also found that COPA did not pass the strict scrutiny test for governmental speech regulations, because while preventing children from accessing harmful material on the Internet was a compelling government interest, the statute was not narrowly tailored enough to enable other users, including consenting adults, to access such material voluntarily, and (given the availability of filtering software) the statute was not the least restrictive means of achieving the government's goals.

[11] While allowing the injunction against the enforcement of COPA to stand, the Supreme Court gave the government one more chance to argue its case, due to the now clarified definitions of "contemporary community standards" and other matters.

Justice Antonin Scalia dissented, arguing that pornography in the media deserved no constitutional protection regardless of the existence of COPA, so that statute should not have been subjected to the strict scrutiny test.

[11] Justice Stephen Breyer delivered another dissent, arguing that COPA was indeed the least restrictive means to achieve the government's compelling interest in shielding children from Internet pornography.

[11] The case was remanded to the Eastern District of Pennsylvania and went to trial again in 2006, at which time the government was given the opportunity to update its arguments in favor of enforcing COPA.