We just touched on the Bill of Rights in American Government, so we wrestled on whether this phrase is absolute in its restriction or if it allows some give (like with falsely shouting fire in a crowded theater).
Some brainy types go at it here:
Note that the First Amendment doesn’t say that Congress shall make no
law restricting speech or press; rather, Congress can’t restrict “the
freedom of speech” and “the freedom of the press.” Maybe that’s just a
fancy way of saying “speech” and “press.” But maybe it suggests that
“the freedom of speech” and “the freedom of the press” were references
to broader legal concepts that were used to refer to limited freedom,
not unlimited freedom. For instance, perhaps the freedom of speech and
of the press were understood as excluding libel and slander, or possibly
even obscenity, threats, and some other kinds of speech.
And here:
. . . perhaps the Founders, being politicians, enacted a broad generality that
they agreed on, even though they had no consensus about exactly what it
meant. I’m pretty certain that they did not mean that “Congress
shall make no law ... abridging the freedom of speech, or of the press”
means that all speech restrictions — or at least all federal speech
restrictions — are unconstitutional, period. Which part of “make no law”
don’t you understand?, some people colorfully argue. Well, I understand
“make no law” just fine, as do those who support the constitutionality
of some speech restrictions. The real difficulty is with “the freedom
of.”
These are worth a quick read if you have the time. What is the difference between "speech" and "freedom of speech?"