I always liked the expression, "Your rights end where someone else's rights begin." You can get arrested for saying something if it infringes on someone else's rights.

A popular example of this is shouting, "FIRE" in a crowded theater. Free speech doesn't protect you here because you put the safety of the rest of the audience at risk by trying to incite a panic.

I would also like to add that some people confuse censorship as an antithesis to Free Speech. This is not inherently so. Every time a moderator deletes spam comments and every time a curse word is bleeped out on TV, this is censorship. Yet, it is not infringing upon Free Speech.

Spam doesn't contribute in any meaningful way, thus it has no value. It clutters the comments section and is cleaned out.

Curse words are considered offensive to common sensibility by some people and profane to the ears of children by most. Because TV is broadcast to a public audience it was agreed reasonable to censor out such words so as to not offend such sensibilities.

Thus speech is silenced but Free Speech is not infringed.