Rep. Nancy Pelosi (D-CA) made an excellent effort when trying to make a point about the limits of free speech in the United States. Unfortunately, she mixed up a few words, saying that the U.S. Constitution doesn't permit people to yell "wolf" in a crowded theater.
While yelling "wolf" in a crowded theater would be pretty strange and I'm not entirely sure when it'd even be a thing someone would do (unless the theater is located in the middle of the woods, maybe?), it's definitely protected by the Constitution. If there actually were a wolf in a theater, it would be 100 percent legal to let people know about said wolf, just as it's 100 percent legal to yell "fire" in a crowded theater if there's actually a fire.
Of course, the things she was going for was either "the boy who cried wolf" (which is a person who fakes a claim for so long that people don't actually believe him when it happens--not at all dissimilar to how the Democrats smeared Mitt Romney as the worst person in the world when he was the nominee.) or "yelling 'fire' in a crowded theater." The decision in Schenck v. United States found that a person could do "dangerous speech" if it's actually true. Further, in this scenario--where the parks service denied people free speech for a rally--the "fire in a crowded theater" example doesn't actually apply unless the people were literally advocating violence.
Maybe Pelosi should actually read the Constitution to find out what's in it. Just a thought.