So, if you go read through all the FBI reports about Black Lives Matters you find references to OMGs. Apparently a lot of various organizations like Outlaw Motorcycle Gangs will use large events like protests as cover.

There's also counter-protesters which will attempt to agitate (they might argue the protesters agitated them) and cause problems.

So, largely protesters cannot be disciplined because not everybody there is actually in agreement as to why they're there.

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That said. It's a public roadway. The proper punishment for driving poorly is a police citation not a bullet.