What authority does the police have to stop or disperse a protest?

To be sure, government officials may stop or disperse a protest when faced with an "immediate threat to public safety, peace, or order," including "interference with traffic upon the public streets." Parmley , 465 F.3d at 57 (quoting Cantwell v. Connecticut , 310 U.S. 296, 308, 60 S.Ct. 900, 84 L.Ed. 1213 (1940) ). But this authority is not without limits. Among other things, officials have an obligation, "absent imminent harm," to inform demonstrators that they must disperse, id. at 60, and may not use unreasonable force, id. at 63. In short, our cases amply establish that protesters enjoy robust constitutional protection, protection of which reasonable law enforcement officers are well aware.