The dispute between the broadcast networks and the Federal Communications Commission is the court's first major broadcast indecency case in 30 years.
At issue is the FCC's policy, adopted in 2004, that even a one-time use of profanity on live television is indecent because some words are so offensive that they always evoke sexual or excretory images. So-called fleeting expletives were not treated as indecent before then.
The words in question begin with the letters "F" and "S." The Associated Press typically does not use them.
Chief Justice John Roberts, the only justice with young children at home, suggested that the commission's policy is reasonable. The use of either word, Roberts said, "is associated with sexual or excretory activity. That's what gives it its force."
Justice John Paul Stevens, who appeared skeptical of the policy, doubted that the f-word always conveys a sexual image.