The legal right to freedom of exrpession is grounded in the First Amendment to the United States Constitution. The first 10 amendments to the constitution make up The Bill of Rights.
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
The links above provide a starting point for exploring the notion of Free Expression. Keep in mind there are many words that can be used to research this topic. Trying different words in each of the databases listed above will provide you with different conceptual overviews from various sources. Each database provides different articles.
Some other words to consider are:
And various aspects of the above such as:
And various specific limits of free expression, including:
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