And the right to peaceably assemble is in the first amendment.
As long as they were peaceable why were they being told to disperse?
And don't start with the "well they could at some point" or "by not dispersing they were no longer peaceful" because I will not buy just by not following orders the police have no right to give you that you become non-peaceful.
Ask the cops. Even peaceable assembly sometimes requires a permit.
The Constitution doesn’t say the cops can’t tell you not to shit in the streets, either, so I guess that’s all good.