WASHINGTON — The government lost its final attempt today to revive a federal law intended to protect children from sexual material and other objectionable content on the Internet.

The Supreme Court said this morning it won't consider reviving the Child Online Protection Act, which lower federal courts struck down as unconstitutional. The law has been embroiled in court challenges since it passed in 1998 and never took effect.

It would have barred Web sites from making harmful content available to minors over the Internet.

A federal appeals court in Philadelphia ruled that would violate the First Amendment, because filtering technologies and other parental control tools are a less restrictive way to protect children from inappropriate content online.

The act was passed the year after the Supreme Court ruled that another law intended to protect children from explicit material online — the Communications Decency Act — was unconstitutional.

The Bush administration had pressed the justices to take the case. They offered no comment on their decision to reject the government's appeal.