It’s private property. The fist amendment protects speech on public property. It’ll be expensive, but if they don’t have the political clout to have publically funded police sufficient to arrest them all then they’ll have to spend $50/hour per cop to get off-duty police. They need to specify black cops only and have 20 of them. They need to have all the laws briefed so those cops can start arresting right away. That should break it up pretty well.
The First Amendment protects free speech and peaceable (not riotous) assembly on public property. Of course, communists like BLM see all property as socialistic and are of the “abolition of private property” mindset.
The Minnesota Supreme Court says no. Since the public paid in the neighborhood of 186 million of the cost to construct it, they say it in no way can be considered private property. And I thought Massachusetts was bad.