Final answer:
The 1st Amendment of the United States Constitution is violated when a law restricts freedom of speech.
Step-by-step explanation:
The amendment that is violated when a law restricts freedom of speech is the 1st Amendment of the United States Constitution. This amendment protects the right to freedom of speech, including the freedom to express ideas and opinions without government interference or censorship. By passing a law that restricts freedom of speech, the government would be infringing upon this constitutional right.
Learn more about Freedom of speech and the 1st Amendment