Conspiracy to impede is unconstitutional, as people in the US have the right to peacefully assemble. If cops decide to illegally break up a protest, then they can say "oh you're impending me!" and no one actually has a 1st amendment right.
“the government may impose reasonable restrictions on the time, place, or manner of protected speech, provided the restrictions ‘are justified without reference to the content of the regulated speech, that they are narrowly tailored to serve a significant governmental interest, and that they leave open ample alternative channels for communication of the information.’”
People complain about this all the time (“free speech zones”) but it’s been the law for decades.
See also https://www.aclu.org/know-your-rights/protesters-rights .
There's a lot of precedent too, I'm sure.
So yeah, there's no real way to know ahead of time if any protest is or is not legal or legally impeded. That's not the case with continental law where it's defined ahead of time.
There is nuance and balance to be had in law, your rights end where others begin.
Isn't this exactly what the MAGA crowd has professed to believe since 1/6/2021?
They were fine storming government buildings with guns in hand during covid. They considered the Bundy brothers and Kyle Rittenhouse to be heroes and patriots.
These rights are absolute and inalienable, granted by God as long as you're "white and right." Otherwise it's time to crack skulls.