美国法律中的言论自由,其范围在Chaplinsky v. New Hampshire, 315 U.S. 568 (1942)一案中阐释的比较清楚。联邦最高法院Frank Murphy在判词中写道
“对于某一类有明确定义且类型受到限定的言论而言,对其的制止和惩罚并不会导致任何的宪法问题。其中包括淫秽色情、亵渎性质、侮辱诽谤和挑衅的言论。此类言论,就其本身性质而言会导致对他人的侵害,或者可能导致对和平秩序的破坏“ (“There are certain well-defined and narrowly limited classes of speech, the prevention and punishment of which have never been thought to raise any constitutional problem. These include the lewd and obscene, the profane, the libelous, and the insulting or "fighting" words those which by their very utterance inflict injury or tend to incite an immediate breach of the peace.”)