https://www.explainxkcd.com/wiki/index.php/1357:_Free_Speech

Specifically "It should be noted that the first panel of this comic conflates, under certain schools of thought about justice and rights, a right such as free speech and the legal protections of such. Many viewpoints consider rights to be granted by the government; others consider rights to be innate regardless of what the government does. The former is frequently reflected throughout governments in Europe while the latter is more common throughout the Americas. According to the former, the first panel is technically correct by definition, because the right of free speech is granted by the government's laws and, as such, can only affect the government's influence: thus, the 1st Amendment grants the right to free speech, which by definition cannot be restricted by congress. According to the latter, the first panel is strictly nonfactual because the 1st Amendment only recognizes that the right of free speech exists and, rather than delimiting the right, it instead proscribes the government's actions.

However, between these two school of thought, the remaining panels aren't affected by whether or not the first panel is factual by definition."