"5. The First Amendment protects us against government limits on our freedom of expression, but it doesn’t prevent a private employer from setting its own rules."
https://www.mtsu.edu/first-amendment/page/things-you-need
"Freedom of speech in the United States"
https://en.wikipedia.org/wiki/Freedom_of_speech_in_the_United_States
https://www.law.cornell.edu/constitution/first_amendment
https://constitutioncenter.org/interactive-constitution/amendment/amendment-i
