Final answer:
The Supreme Court invalidated the Communications Decency Act because it violated the First Amendment of the U.S. Constitution, due to its broad and vague provisions that suppressed free speech.
Step-by-step explanation:
The primary ground for the court to invalidate the Communications Decency Act was that it violated the First Amendment of the U.S. Constitution, which guarantees freedom of speech. The U.S. Supreme Court found that the Act's provisions were too broad and vague, and they suppressed a significant amount of free speech without adequately serving a compelling government interest. This violated the requirement for regulations to be narrowly tailored to serve an important government interest, without unduly burdening free speech.
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